JP7204593B2 - Method of operating Rankine cycle system and waste heat recovery device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of operating a Rankine cycle system and a waste heat recovery apparatus having the Rankine cycle system, and more particularly to a technology for improving the waste heat regeneration efficiency of the Rankine cycle.

A Rankine cycle system has a circulation circuit of a working fluid via an evaporator and a condenser. is condensed by a condenser. In order to improve the energy efficiency of the entire vehicle, this Rankine cycle system was introduced as a means of recovering waste heat from the internal combustion engine. It is known to generate electricity (Patent Document 1).

JP 2015-232273 A (paragraph 0023)

In the Rankine cycle system, in order to obtain sufficient waste heat regeneration efficiency from the viewpoint of improving energy efficiency, it is necessary to ensure the cooling capacity of the condenser. However, if an attempt is made to secure a cooling capacity by air cooling, there is a concern that the size of the condenser will increase. In the case of in-vehicle use, it is often difficult to install a large air-cooled condenser due to the limitation of installation space, and the cooling capacity tends to be insufficient. On the other hand, even if the condenser is water-cooled and the heat medium that passes through the condenser is cooled by the radiator, the use of an existing in-vehicle radiator such as a radiator does not provide the function that the radiator should originally perform. Sufficient cooling capacity is not always available with Rankine cycle systems due to the need to reserve.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to make it possible to secure a relatively large cooling capacity in a Rankine cycle system and a waste heat recovery apparatus including the same, thereby contributing to improvement in waste heat recovery efficiency.

In one form of the invention, a Rankine cycle system comprising an evaporator for evaporating a working fluid and a condenser located downstream of the evaporator in the direction of flow of the working fluid for condensing vapors of the working fluid. A method of operation is provided. An evaporator is provided in a first circuit of a first heat medium through a heat source, the first heat medium heated by the heat source being cooled by a first radiator, and an evaporator by the first heat medium. A working fluid is heatably connected. Then, during operation of the Rankine cycle system that circulates the working fluid to the evaporator and the condenser, the second heat medium is circulated in parallel with the flow of the first heat medium between the condenser and the first radiator, A second circuit of the second heat medium is formed, and the heat recovered by the condenser by the second heat medium is radiated by the first radiator.

In another form, a waste heat recovery system having a Rankine cycle system is provided.

When the Rankine cycle system is in operation, the heat of the first heat medium is taken away by the working fluid of the Rankine cycle system through the evaporator, so the cooling capacity of the first radiator has a margin, or the first heat is generated by the first radiator. Cooling itself of the medium becomes unnecessary. Therefore, when the Rankine cycle system is in operation, a second circuit of a second heat medium is formed that connects the condenser and the first radiator, and the heat recovered by the condenser is radiated by the first radiator. Then, by allocating the surplus of the cooling capacity of the first radiator to the release of the heat recovered by the condenser, it becomes easy to secure a large cooling capacity, and the waste heat regeneration efficiency is improved. becomes possible.

FIG. 1 is a schematic diagram showing the overall configuration of a waste heat recovery device according to one embodiment of the present invention. FIG. 2 is an explanatory diagram showing the operation of the same waste heat recovery device when the Rankine cycle system is stopped. FIG. 3 is an explanatory diagram showing the operation of the same waste heat recovery device when the Rankine cycle system is in operation. FIG. 4 is a flow chart for explaining the operation of the waste heat recovery system. FIG. 5 is a schematic diagram showing the configuration of a high-temperature coolant circuit and a low-temperature coolant circuit applicable to the same waste heat recovery device, and also shows the flow of the heat medium when the Rankine cycle system is stopped. FIG. 6 is a schematic diagram showing the flow of the heat medium in the high temperature coolant circuit and the low temperature coolant circuit during operation of the Rankine cycle system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the overall configuration of a waste heat recovery device 1 according to one embodiment of the present invention.

A waste heat recovery device (hereinafter simply referred to as "waste heat recovery device") 1 according to the present embodiment includes a Rankine cycle system S, and the waste heat generated by the heat source 11 is recovered through the Rankine cycle system S. Configured. In this embodiment, the waste heat recovery device 1 is mounted on a hybrid vehicle and uses the internal combustion engine 11 that constitutes the drive source thereof as a heat source. converted to and collected. The form of the drive source may be a series type or a parallel type, and in this embodiment, it is a series type.

The Rankine cycle system S comprises an evaporator 21 and a condenser 22, and the working fluid flows through these thermal devices 21, 22 in that order. In this embodiment, a heater 23 is further provided as an additional element between the evaporator 21 and the condenser 22, and when the pump 24 operates, the working fluid flows into the evaporator 21, the heater 23 and the condenser 22. and circulates through the Rankine cycle system S with its phase change. That is, the working fluid is a liquid under standard conditions (for example, 25° C. and 1 atm), is discharged from the pump 24, is evaporated by the evaporator 21, is further heated by the heater 23, and is A further temperature increase is achieved. Then, the expander 25 is operated, and then the liquid is condensed in the condenser 22 to return to the original liquid. Although not shown, the working fluid passage includes a passage that bypasses the expander 25 during the priming operation of the Rankine cycle system S and a valve that closes the bypass passage during regeneration. Equipped with various sensors that

A turbine can be exemplified as the expander 25 applicable to the present embodiment. This turbine converts the energy of the steam into mechanical work (that is, rotational power), drives a generator to generate electricity, supplies the electric motor that is the driving source, and charges the battery. It is possible to The work performed by the expander 25 can be converted into other forms of energy, and can also be used as mechanical work. For example, the work of the expander 25 can assist the running power of the vehicle.

The waste heat recovery device 1 comprises a hot coolant circuit Ch as a means of providing heat to the Rankine cycle system S, in particular its evaporator 21 and heater 23 . Furthermore, the waste heat recovery device 1, in the condenser 22 of the Rankine cycle system S, as means for recovering the heat possessed by the working fluid, which is steam, is a low-temperature cooling system that circulates a heat medium having a temperature lower than that of the high-temperature coolant circuit Ch. A liquid circuit Cl is provided. In the present embodiment, the high-temperature coolant circuit Ch and the low-temperature coolant circuit Cl are both cooling circuits of the drive source, and correspond to the "high-temperature circuit" and the "low-temperature circuit" according to the present embodiment, respectively.

The high-temperature coolant circuit Ch is a circuit that circulates a coolant (hereinafter sometimes referred to as a "high-temperature coolant") as a "first heat medium". In order to distinguish it from the "low temperature radiator" to be described later, a high temperature radiator 12 is interposed. The high-temperature radiator 12 corresponds to the "first radiator" according to the present embodiment, and the high-temperature coolant circuit Ch is basically a high-temperature coolant (specifically, is configured as a circuit for circulating the engine cooling water) and radiating the heat received by the high-temperature coolant from the internal combustion engine 11 through the high-temperature radiator 12 .

Here, a high-temperature coolant circuit Ch is connected to the evaporator 21 and the heater 23 of the Rankine cycle system S so that the working fluid can be heated by the high-temperature coolant passed through the internal combustion engine 11 and heated. Specifically, the evaporator 21 and the heater 23 are both configured as heat exchangers, and a conduit that is part of the hot coolant circuit Ch is drawn into the evaporator 21 and the heater 23 to By passing through, the heated high-temperature cooling liquid functions as a high-temperature fluid, and the working fluid functions as a low-temperature fluid, and the working fluid is heated by heat exchange between them. The hot radiator 12 is arranged downstream of the heater 23 in the direction of flow of the hot coolant.

On the other hand, the low-temperature coolant circuit Cl is a circuit that circulates a coolant whose temperature is lower than that of the high-temperature coolant (hereinafter sometimes referred to as a "low-temperature coolant") as a "second heat medium". A radiator (hereinafter referred to as a "low temperature radiator") 16 having a cooling capacity smaller than that is interposed. The low-temperature coolant circuit Cl includes an electric motor 17 as a drive source to be cooled. It is configured as a circuit that dissipates the heat received by cooling the electric motor 17 with the low-temperature radiator 16 . An inverter may be employed in place of or in addition to the electric motor 17 as the object to be cooled by the low-temperature coolant circuit Cl.

Here, the low-temperature coolant circuit Cl is a circuit that circulates a heat medium independently from the high-temperature coolant circuit Ch, and is basically in a thermally separated state. The coolant circulated in the low-temperature coolant circuit Cl and the coolant circulated in the high-temperature coolant circuit Ch may be the same type of coolant or different types of coolant. In this embodiment, the same engine coolant as that used in the high-temperature coolant circuit Ch is used as the coolant in the low-temperature coolant circuit Cl.

Furthermore, a low-temperature coolant circuit Cl is connected to the condenser 22 of the Rankine cycle system S so that the heat of the working fluid can be recovered by the low-temperature coolant that has passed through the low-temperature radiator 16 and cooled. Specifically, like the evaporator 21 etc., the condenser 22 is also configured as a heat exchanger, and a conduit, which is part of the cryogenic coolant circuit Cl, is drawn into the condenser 22 and passes through it. The steam working fluid functions as a high-temperature fluid, and the low-temperature coolant after cooling functions as a low-temperature fluid, and the working fluid is cooled by heat exchange between the two.

In addition to the above, pumps 13 and 18 are interposed in the high-temperature coolant circuit Ch and the low-temperature coolant circuit Cl, respectively, as means for pumping the heat medium. An EGR cooler 14 is interposed as a separate means for recovering the . The EGR cooler 14 is interposed between the evaporator 21 and the heater 23 in the high-temperature coolant circuit Ch. heat again by heat exchange.

In the present embodiment, the high-temperature coolant circuit Ch is provided with a bypass flow path Pb that directly communicates the inlet side and the outlet side of the high-temperature radiator 12 and causes the high-temperature coolant to bypass the high-temperature radiator 12. . The bypass flow path Pb shown in FIG. 1 is conceptual and is not only a bypass dedicated flow path, but also blocks the flow of the hot coolant toward the high temperature radiator 12 and cuts off the flow in the other partial flow paths. By increasing it, it is possible to substantially achieve it. Further, a flow path switching valve v1 is installed in the main flow path Pm of the high temperature coolant circuit Ch via the high temperature radiator 12 . The function of the flow path switching valve v1 will be described later.

Further, in the present embodiment, the low-temperature coolant flowing through the low-temperature coolant circuit Cl is connected between the main flow path Pm of the high-temperature coolant circuit Ch and the low-temperature coolant circuit Cl to the high-temperature radiator 12 provided in the main flow path Pm. Guide channels Pg1 and Pg2 are arranged so as to be able to introduce. Specifically, a first guide passage Pg1 branched from the low-temperature coolant circuit Cl and connected to the high-temperature coolant circuit Ch on the inlet side of the high-temperature radiator 12, and a first guide channel Pg1 on the outlet side of the high-temperature radiator 12 from the high-temperature coolant circuit Ch. and a second guide flow path Pg2 that branches off and joins the low-temperature coolant circuit Cl downstream of the branch point of the first guide flow path Pg1. When the guide channels Pg1 and Pg2 are opened, they cooperate with the main channel Pm to direct the partial channel in which the heat source (electric motor) 17 on the low temperature side of the low temperature coolant circuit Cl is interposed. , forming parallel flow paths to connect the hot radiator 12 and the cold radiator 16 in series with respect to the flow of the cold coolant. However, the guide passages Pg1 and Pg2 are required to introduce the low-temperature coolant of the low-temperature coolant circuit Cl into the high-temperature radiator 12 and enable the low-temperature coolant to circulate between the condenser 22 and the high-temperature radiator 12. That is. Therefore, the arrangement of the guide channels Pg1 and Pg2 is not limited to this, and the relationship between the high temperature radiator 12 and the low temperature radiator 16 may be in series or in parallel.

The previously described flow path switching valve v1 is installed at the branch of the second guide flow path Pg2 from the high temperature coolant circuit Ch. It switches between the main flow path Pm of the liquid circuit Ch and the second guide flow path Pg2. Along with this, an on-off valve (hereinafter referred to as “first on-off valve”) v21 is interposed upstream of the high-temperature radiator 12 in the main flow path Pm. Allow or block the introduction of hot coolant.

Further, an on-off valve (hereinafter referred to as a "second on-off valve") v22 is installed in the first guide passage Pg1 to allow and block the introduction of the low-temperature coolant flowing through the low-temperature coolant circuit Cl into the high-temperature radiator 12. there is Here, the flow path switching valve v1 and the first and second on-off valves v21 and v22 constitute "switching valves" according to the present embodiment.

The controller 101 controls the operation of the channel switching valve v1 and the on-off valves v21 and v22. The controller 101 is configured as an electronic control unit, and is configured by a microcomputer having a central processing unit (CPU), various storage units such as ROM and RAM, an input/output interface, and the like. The controller 101 calculates operation amounts for these valve devices v1, v21, and v22 based on input information from various sensors provided so as to detect the operating state of the vehicle, and outputs command signals according to the operation amounts. Output to the actuator. In this embodiment, the driving state sensors include a vehicle speed sensor 111 that detects the vehicle speed VSP, and a first coolant temperature sensor that detects the high-temperature circuit water temperature Twh, which is the temperature of coolant (engine coolant) flowing through the high-temperature coolant circuit Ch. 112. A second coolant temperature sensor 113 is provided for detecting a low-temperature circuit water temperature Twl, which is the temperature of the coolant (engine coolant) flowing through the low-temperature coolant circuit Cl.

As described above, the Rankine cycle system S needs to ensure the cooling capacity of the condenser 22 in order to obtain sufficient waste heat regeneration efficiency from the viewpoint of improving energy efficiency. However, if an attempt is made to secure a cooling capacity by air cooling, the overall size of the condenser 22 including the heat radiating portion cannot be avoided. On the other hand, even if a water-cooled low-temperature radiator 16 is used, the required cooling capacity cannot be satisfied because the low-temperature radiator 16 has a small cooling capacity, resulting in a shortage of cooling capacity.

Therefore, in this embodiment, when the Rankine cycle system S is operated, the high-temperature radiator 12 is incorporated into the coolant circuit on the low-temperature side, and the heat recovered by the condenser 22 is released by the high-temperature radiator 12 in addition to the low-temperature radiator 16. Also, a larger cooling capacity can be secured than when only the low-temperature radiator 16 is used.

2 and 3 show the operation of the waste heat recovery device 1 according to this embodiment, FIG. 2 shows the operation when the Rankine cycle system S is stopped, and FIG. 3 shows the operation when the Rankine cycle system is in operation. respectively shown.

When the Rankine cycle system S is stopped ( FIG. 2 ), the pump 24 is stopped and circulation of the working fluid in the Rankine cycle system S is stopped. By operating the pumps 13 and 18 of the high-temperature coolant circuit Ch and the low-temperature coolant circuit Cl, opening the first on-off valve v21 and closing the second on-off valve v22, the main flow of the high-temperature coolant circuit Ch is Break the connection between the path Pm and the cryogenic coolant circuit Cl. As a result, the high-temperature coolant in the high-temperature coolant circuit Ch and the low-temperature coolant in the low-temperature coolant circuit Cl independently circulate through the respective circuits Ch and Cl, and waste heat from the internal combustion engine 11 is released by the high-temperature radiator 12. while the waste heat from the electric motor 17 is radiated by the cold radiator 16 . In the high-temperature coolant circuit Ch, the flow path switching valve v1 sets the connection destination of the high-temperature radiator 12 to the main flow path Pm, and most of the high-temperature coolant heated by the internal combustion engine 11 is introduced into the high-temperature radiator 12. . Here, the circulation circuit of the coolant on the high temperature side formed between the internal combustion engine 11 which is the heat source and the high temperature radiator 12 when the Rankine cycle system S is stopped corresponds to the "first circuit of the first heat medium". .

On the other hand, when the Rankine cycle system S is in operation (FIG. 3), the pump 24 is operated to circulate the working fluid through the evaporator 21, the heater 23 and the condenser 22, and pass through the evaporator 21 and the heater 23. The energy of the working fluid vapor is recovered as work by the expander 25 . Both the pumps 13 and 18 of the high-temperature cooling liquid circuit Ch and the low-temperature cooling liquid circuit Cl are operated in the same manner as when stopped. is opened, the low-temperature coolant circuit Cl is communicated with the high-temperature radiator 12 . As a result, the coolant flowing through the low-temperature coolant circuit Cl can be introduced into the high-temperature radiator 12 via the first and second guide passages Pg1 and Pg2, and circulated between the condenser 22 and the high-temperature radiator 12. Become. The flow path switching valve v1 sets the connection destination of the high temperature radiator 12 to the second guide flow path Pg2, the high temperature radiator 12 is separated from the main flow path Pm of the high temperature coolant circuit Ch, and the high temperature radiator after being heated by the internal combustion engine 11 The coolant is guided to the bypass flow path Pb and bypasses the high temperature radiator 12 . Here, the circulation circuit of the coolant on the low temperature side formed between the condenser 22 and the high temperature radiator 12 when the Rankine cycle system S is in operation corresponds to the "second circuit of the second heat medium".

FIG. 4 is a flow chart showing the content of control performed by the controller 101 according to this embodiment. The controller 101 is programmed to execute the control shown in FIG. 4 at predetermined time intervals after power-on activation.

In S101, the vehicle speed VSP, the high-temperature circuit water temperature Twh, and the low-temperature circuit water temperature Twl are read as various input information indicating the operating state of the vehicle.

In S102, it is determined whether or not the Rankine cycle system S is in operation. If it is in operation, the process proceeds to S108, and if it is not in operation, that is, when the Rankine cycle system S is stopped, the process proceeds to S103.

In S103-105, it is determined whether or not the operating conditions of the Rankine cycle system S are satisfied. The operation of the Rankine cycle system S is permitted only when all the conditions of S103 to S105 are satisfied, and the operation of the Rankine cycle system S is prohibited or suspended when any one of the conditions is not satisfied. .

In S103, it is determined whether or not the vehicle speed VSP is equal to or higher than a predetermined speed VSP1. This is because it is necessary for the high temperature radiator 12 and the low temperature radiator 16 to function to receive a considerable amount of running wind. If the vehicle speed VSP is equal to or higher than the predetermined speed VSP1, the routine proceeds to S104.

In S104, it is determined whether or not the high-temperature circuit water temperature Twh is equal to or higher than a predetermined temperature Th1. The predetermined temperature Th1 is a temperature necessary for the evaporator 21 to evaporate the working fluid, and in the present embodiment, is set at 80° C., for example, as a temperature at which it can be determined whether the internal combustion engine 11 has been warmed up. If the high-temperature circuit water temperature Twh is equal to or higher than the predetermined temperature Th1, the routine proceeds to S105, and if it is lower than the predetermined temperature Th1, the current routine is terminated to suspend the operation of the Rankine cycle system S.

In S105, it is determined whether or not the low-temperature circuit water temperature Twl is equal to or lower than the first predetermined temperature Tl1. The first predetermined temperature Tl1 is for determining that the low-temperature coolant is in a temperature range necessary for cooling the electric motor 17, which is the original cooling target of the low-temperature coolant circuit Cl. In the form, the temperature is set to, for example, 55° C. as a temperature with a certain amount of margin for the maximum temperature in such a range. If the low-temperature circuit water temperature Twl is equal to or lower than the first predetermined temperature Tl1, the routine proceeds to S106. .

In S106, the pump 24 is operated and the Rankine cycle system S is operated.

In S107, the first on-off valve v21 is closed and the second on-off valve v22 is opened. Set to circuit Cl. As a result, the low-temperature coolant circuit Cl is communicated with the high-temperature radiator 12, and the high-temperature radiator 12 is separated from the main flow path Pm of the high-temperature coolant circuit Ch. Then, by setting a flag indicating that the Rankine cycle system S is in operation, control proceeds from S102 to S108.

In S108, it is determined whether or not the low-temperature circuit water temperature Twl is equal to or lower than the second predetermined temperature Tl2. The second predetermined temperature Tl2 is set to a temperature lower than the first predetermined temperature Tl1 as a temperature indicating that the temperature of the low-temperature coolant is increasing and the cooling of the electric motor 17 is becoming difficult. If the low-temperature circuit water temperature Twl is equal to or lower than the second predetermined temperature Tl2, the current routine is terminated so as to continue operating the Rankine cycle system S. If it is higher than the second predetermined temperature Tl2, the process proceeds to S109.

In S109, it is determined whether or not the low-temperature circuit water temperature Twl is equal to or lower than the third predetermined temperature Tl3. The third predetermined temperature Tl3 is set to a temperature higher than the second predetermined temperature Tl2 as a temperature indicating that the temperature of the low-temperature coolant has further increased and the cooling of the electric motor 17 has become significantly hindered. be. In this embodiment, hysteresis is provided between the first predetermined temperature Tl1 and the third predetermined temperature Tl3, and the third predetermined temperature Tl3 is set to a temperature higher than the first predetermined temperature Tl1. If the low-temperature circuit water temperature Twl is equal to or lower than the third predetermined temperature Tl3, the process proceeds to S110, and if higher than the third predetermined temperature Tl3, the process proceeds to S112.

At S110, the waste heat recovery capacity of the Rankine cycle system S is limited. For example, by reducing the discharge flow rate of the pump 24, the circulation flow rate of the working fluid in the Rankine cycle system S is reduced.

In S111, the first on-off valve v21 is opened, the second on-off valve v22 is closed, and the connection destination of the high-temperature radiator 12 is set to the main flow path Pm of the high-temperature coolant circuit Ch by the flow path switching valve v1. . This separates the low-temperature coolant circuit Cl from the main flow path Pm of the high-temperature coolant circuit Ch, and incorporates the high-temperature radiator 12 into the high-temperature coolant circuit Ch with respect to the flow of the high-temperature coolant. As a result, the high-temperature coolant heated by the internal combustion engine 11 is introduced into the high-temperature radiator 12 again, and the heat is released by the high-temperature radiator 12 .

In S112, the pump 24 is stopped and the Rankine cycle system S is stopped.

5 and 6 schematically show configurations of the high-temperature coolant circuit Ch and the low-temperature coolant circuit Cl of the internal combustion engine 11 applicable to the waste heat recovery system 1 according to this embodiment, and FIG. FIG. 6 shows the flow of the heat medium when the S is stopped, and the flow of the heat medium when the S is in operation, together with arrows.

The high-temperature coolant circuit Ch includes a heating cabin heater 31, a throttle chamber 32, a turbocharger 32 ( An oil cooler 34 and an intercooler 35 are provided as elements to which the high-temperature coolant is directly supplied without passing through the coolant passage 11p, in addition to the exhaust turbine) and the EGR cooler 14 being provided. The high-temperature coolant discharged from the pump 13 and distributed to each of these parts is combined after each part is cooled (heated for the cabin heater 31 and the throttle chamber 32), and pumped by the pump 13 again. Here, the evaporator 21 and the heater 23 of the Rankine cycle system S are both arranged downstream of the internal combustion engine 11 (especially its main body) in the direction of flow of the high-temperature cooling water, and the evaporator 21 is the cabin heater. A heater 23 is arranged downstream of 31 and downstream of the EGR cooler 14, respectively. FIG. 5 conceptually shows the flow path for circulating the working fluid of the Rankine cycle system S by a thick dotted line. After passing through the device 23 in this order, it passes through the condenser 22 which will be described later.

The high-temperature coolant circuit Ch further includes a reservoir tank 36 in which high-temperature coolant is stored and a high-temperature radiator 12 . In this embodiment, the reservoir tank 36 and the hot radiator 12 are arranged in parallel with each other with respect to the flow of hot coolant and are also in parallel with the previously mentioned hot coolant supplied elements.

The low-temperature coolant circuit Cl is provided with an electric motor 17 as an object to be cooled, and also includes a reservoir tank 37 storing a low-temperature coolant and a low-temperature radiator 16 . The low-temperature coolant discharged from the pump 18 is supplied to the electric motor 17, and after cooling the electric motor 17, it is introduced into the low-temperature radiator 16 via the reservoir tank 37 and cooled. The condenser 22 of the Rankine cycle system S is in parallel with the electric motor 17 with respect to the cryogenic coolant flow.

When the Rankine cycle system S is stopped, the flow path switching valve v1 sets the connection destination of the high temperature radiator 12 to the main flow path Pm of the high temperature coolant circuit Ch, and the first on-off valve v21 is opened to reduce the high temperature. While the cooling liquid is permitted to flow into the high temperature radiator 12, the second on-off valve v22 is closed to prohibit the low temperature cooling liquid from flowing into the high temperature radiator 12. FIG.

FIG. 6 shows the flow of the heat medium during operation of the Rankine cycle system S in the high-temperature coolant circuit Ch and the low-temperature coolant circuit Cl according to this embodiment.

When the Rankine cycle system S is in operation, the first on-off valve v21 is closed to prohibit the high-temperature coolant from flowing into the high-temperature radiator 12. The second guide flow path Pg2 is set, and the second on-off valve v22 is opened to allow the low-temperature coolant to flow into the high-temperature radiator 12 .

The waste heat recovery device according to this embodiment is configured as described above, and the actions and effects obtained by this embodiment will be described below.

First, when the Rankine cycle system S is in operation, the evaporator 21 absorbs the heat of the high-temperature coolant, so the cooling capacity of the high-temperature radiator 12 has some margin, or the high-temperature coolant itself cannot be cooled by the high-temperature radiator 12. becomes unnecessary. Therefore, by forming a second circuit of the low-temperature coolant through the high-temperature radiator 12 and allowing the heat recovered in the condenser 22 by the low-temperature coolant to be dissipated by the high-temperature radiator 12, in other words, the Rankine cycle system S By allocating the surplus of the cooling capacity generated in the high-temperature radiator 12 by the operation of the condenser 22 to release the heat recovered by the condenser 22, it becomes easy to secure a large cooling capacity, and the waste heat regeneration efficiency is improved. becomes possible.

Here, when the Rankine cycle system S is operated, the high-temperature radiator 12 is separated from the main flow path Pm of the high-temperature coolant circuit Ch, and the high-temperature coolant flows by bypassing the high-temperature radiator 12, so that the high-temperature coolant circuit Ch and low-temperature coolant circuit Cl, respectively.

Further, the heat recovered by the condenser 22 by the low-temperature coolant can be dissipated not only by the high-temperature radiator 12 but also by the low-temperature radiator 16, thereby ensuring a larger cooling capacity.

Second, by operating the Rankine cycle system S only when the temperature Twl of the low-temperature coolant is equal to or lower than the first predetermined temperature Tl1, the cooling capacity originally required for the low-temperature coolant (specifically, the electric cooling of the motor 17) can be ensured.

Third, during the operation of the Rankine cycle system S, when the temperature Twl of the low-temperature coolant rises and exceeds the second predetermined temperature Tl2, the waste heat regeneration capacity of the Rankine cycle system S is reduced, It is possible to achieve a fail-safe when the heat recovery by the low-temperature coolant is becoming excessive. Here, in the present embodiment, the low-temperature coolant circuit Cl is separated from the main flow path Pm of the high-temperature coolant circuit Ch, and the circulation of the low-temperature coolant through the second circuit is stopped. Although the radiator 12 does not contribute and the cooling capacity is reduced, since the waste heat regeneration capacity is reduced, it can be dealt with by another radiator (that is, the low-temperature radiator 16).

On the other hand, when the temperature Twl of the low-temperature coolant exceeds the second predetermined temperature Tl2, the high-temperature radiator 12 is incorporated (that is, restored) in the high-temperature coolant circuit Ch, and the high-temperature coolant can be cooled by the high-temperature radiator 12. As a result, it becomes possible to compensate for the reduction in the waste heat regeneration capacity with the cooling effect of the high-temperature coolant.

Fourth, when the temperature Twl of the low-temperature coolant further increases and exceeds the third predetermined temperature Tl3, the Rankine cycle system S is stopped. It is possible to avoid excessive trouble in cooling the electric motor 17, which is the object of cooling of the main body.

In the above description, when the Rankine cycle system S is in operation, the heat recovered by the condenser 22 from the low-temperature coolant is released by both the high-temperature radiator 12 and the low-temperature radiator 16. It is also possible to dissipate heat only by the high temperature radiator 12 .

Although the embodiments of the present invention have been described above, the above embodiments merely show a part of the application examples of the present invention, and the technical scope of the present invention is limited to the specific configurations of the above embodiments. not on purpose. Various changes and modifications can be made to the above-described embodiment within the scope of matters described in the claims.

1... Waste heat recovery device 11... Heat source (internal combustion engine)
DESCRIPTION OF SYMBOLS 12... High temperature radiator 16... Low temperature radiator 17... Electric motor 21... Evaporator 22... Condenser 23... Heater 25... Expander S... Rankine cycle system Ch... High temperature coolant circuit Cl... Low temperature coolant circuit Pm... Main flow path Pb Bypass flow path Pg1, Pg2 Guide flow path v1 Flow path switching valve v21, v22 Open/close valve

Claims (10)

an evaporator for evaporating the working fluid;
a condenser arranged downstream of the evaporator in the direction of flow of the working fluid for condensing the vapor of the working fluid;
A method of operating a Rankine cycle system comprising
The evaporator is connected to the first circuit of the first heat medium through a heat source, the first heat medium heated by the heat source being cooled by a first radiator. 1 connecting the working fluid so that it can be heated by a heat medium;
During operation of the Rankine cycle system that circulates the working fluid through the evaporator and the condenser,
forming a second circuit of the second heat medium between the condenser and the first radiator, circulating the second heat medium in parallel with the flow of the first heat medium;
The heat recovered by the condenser by the second heat medium is radiated by the first radiator;
How to operate a Rankine cycle system. During operation of the Rankine cycle system, the first heat medium is flowed by bypassing the first radiator;
A method of operating the Rankine cycle system according to claim 1 . The second circuit includes a second radiator,
During operation of the Rankine cycle system, the heat recovered by the second heat medium is radiated by the first radiator and the second radiator;
A method for operating the Rankine cycle system according to claim 1 or 2. The second heat medium circulating in the second circuit has a lower temperature than the first heat medium circulating in the first circuit,
A method for operating the Rankine cycle system according to any one of claims 1 to 3. detecting the temperature of the second heat medium;
operating the Rankine cycle system when the detected temperature of the second heat medium is equal to or lower than a first predetermined temperature;
stopping the Rankine cycle system if the detected temperature exceeds the first predetermined temperature;
A method for operating the Rankine cycle system according to any one of claims 1 to 4. reducing waste heat regeneration capacity of the Rankine cycle system when the detected temperature exceeds a second predetermined temperature lower than the first predetermined temperature during operation of the Rankine cycle system;
A method for operating the Rankine cycle system according to claim 5 . stopping the Rankine cycle system when the detected temperature reaches a third predetermined temperature higher than the second predetermined temperature during operation of the Rankine cycle system;
A method for operating the Rankine cycle system according to claim 6 . circulating the first heat medium through the first radiator when reducing the waste heat regeneration capacity;
A method for operating the Rankine cycle system according to claim 6 or 7. an evaporator that evaporates a working fluid; an expander that receives the vapor of the working fluid evaporated by the evaporator; a Rankine cycle system comprising a condenser for condensing steam;
A high-temperature circuit for circulating a first heat medium through a heat source,
A first radiator interposed so as to be able to cool the first heat medium heated by the heat source,
a high-temperature circuit in which the evaporator is connected so as to be able to heat the working fluid with the first heat medium;
A low-temperature circuit configured independently of the high-temperature circuit and configured to circulate a second heat medium, wherein the condenser is connected to the low-temperature circuit so that heat of the working fluid can be recovered by the second heat medium. ,
A guide passage extending from the low-temperature circuit and disposed so as to introduce the second heat medium into the first radiator, the switching valve provided in or attached to the guide passage. wherein the switching valve includes a guide flow path that allows the first heat medium or the second heat medium to selectively flow into the first radiator;
a controller that controls the operation of the switching valve;
A waste heat recovery device. a Rankine cycle system comprising an evaporator for evaporating a working fluid and a condenser positioned downstream of the evaporator in the direction of flow of the working fluid for condensing a vapor of the working fluid;
A first circuit of a first heat medium through a heat source, comprising a first radiator interposed so as to be able to cool the first heat medium heated by the heat source, wherein the evaporator receives the first heat. a first circuit connected by a medium so as to be able to heat the working fluid;
with
In a first operation mode for stopping the Rankine cycle system, the heat given to the first heat medium by the heat source is radiated by the first radiator through the first circuit,
In a second mode of operation for operating the Rankine cycle system,
forming a second circuit of the second heat medium between the condenser and the first radiator, circulating the second heat medium in parallel with the flow of the first heat medium;
The heat recovered by the condenser by the second heat medium is dissipated by the first radiator through the second circuit;
Waste heat recovery equipment.

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