JP2009074494A - Exhaust heat recovery device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust heat recovery device having high heat recovery performance and capable of preventing local boiling of engine cooling water. <P>SOLUTION: The exhaust heat recovery device is provided with a water tank 31 interposed on an exhaust heat recovery circuit 21 for circulating the engine cooling water; an inlet pipe 32 provided in the water tank 31 and guiding the engine cooling water in the exhaust heat recovery circuit 21 to inside of the water tank 31; an outlet pipe 33 provided above the inlet pipe 32 and leading out the engine cooling water inside the water tank 31 to the exhaust heat recovery circuit 21; an evaporating part 40 for heating and evaporating working fluid filled therein by heat exchange with exhaust heat; a condensing part 50 for cooling and condensing working fluid by heat exchange between the evaporated working fluid and the engine cooling water inside the water tank 31 and heating the engine cooling water; a steam pipe 60 for making the working fluid evaporated in the evaporating part 40 flow into the condensing part 50; and a recirculation pipe 61 for recirculating the working fluid condensed in the condensing part 50 to the evaporating part 40. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust heat recovery device that recovers exhaust heat discharged from an internal combustion engine and heats a fluid to be heated.

Patent Document 1 discloses a loop heat pipe heat exchanger. This heat exchanger is disposed above the evaporation unit that evaporates the working fluid sealed inside by heat input from the outside, and is heated between the working fluid evaporated by the evaporation unit and the fluid to be heated. And a condensing unit that cools and condenses the working fluid and heats the fluid to be heated. The evaporation unit and the condensation unit are annularly connected by a vapor line and a condensation line. The working fluid evaporated in the evaporating part flows into the condensing part through the vapor line, and the working fluid condensed in the condensing part flows into the evaporating part through the condensing line.
JP-A-4-45393

  The heat pipe heat exchanger described above can be applied to an exhaust heat recovery device that recovers exhaust heat discharged from an engine of a vehicle and heats engine cooling water. FIG. 5 is a cross-sectional view schematically showing a configuration in the vicinity of the condensing unit in the exhaust heat recovery apparatus including a loop heat pipe. The vertical direction in FIG. 5 generally represents the vertical vertical direction. The thin solid arrow in FIG. 5 represents the flow direction of the working fluid in the liquid state, the broken arrow represents the flow direction of the working fluid in the gaseous state, and the thick arrow represents the flow direction of the engine coolant.

  As shown in FIG. 5, the heat pipe condensing unit 140 is provided in a water tank 131 interposed in the middle of a cooling water circuit through which engine cooling water circulates. On the side surface of the water tank 131, there are provided an inlet pipe 132 for introducing the engine cooling water flowing through the cooling water circuit into the water tank 131, and an outlet pipe 133 for leading the engine cooling water in the water tank 131 to the cooling water circuit. It has been. The inlet pipe 132 is provided at the upper part of the side surface of the water tank 131, and the outlet pipe 133 is provided below the inlet pipe 132.

  In the case of the above configuration, if a gas such as air is mixed in the engine coolant passing through the water tank 131, the gas (bubbles) 134 accumulates in the upper part of the water tank 131. If the gas 134 accumulates in the water tank 131, the condensing performance of the condensing unit 140 is reduced, so that the working fluid is difficult to return to the evaporating unit. Therefore, there arises a problem that the heat recovery performance of the exhaust heat recovery device is deteriorated.

  In general, the engine cooling water is circulated in the cooling water circuit by an engine-driven water pump. Therefore, when the engine is stopped, the circulation of the engine cooling water is also stopped. At the time of dead soak immediately after the engine is stopped, the engine coolant in the water tank 131 in which the circulation is stopped is heated by the heat transfer from the evaporation unit that continuously recovers the remaining heat. On the other hand, when the gas 134 is accumulated in the water tank 131, the engine cooling water in the water tank 131 is reduced, so that the heat capacity is reduced. Therefore, there arises a problem that the possibility that the engine cooling water will boil locally in the water tank 131 during the dead soak.

  An object of the present invention is to provide an exhaust heat recovery device that has high heat recovery performance and can prevent local boiling of a fluid to be heated.

  In order to achieve the above object, the present invention employs the following technical means.

  The invention according to claim 1 is an exhaust heat recovery device that recovers exhaust heat of exhaust exhausted from the internal combustion engine (10) to heat the heated fluid, and a heated fluid circuit that circulates the heated fluid A heated fluid tank (31) interposed in (21) and a heated fluid tank (31), and the heated fluid of the heated fluid circuit (21) is introduced into the heated fluid tank (31). The heated portion in the heated fluid tank (31) is led out to the heated fluid circuit (21). The introduced portion (32) is provided above the introduced portion (32) of the heated fluid tank (31). And the evaporating unit (40) for heating and evaporating the working fluid enclosed therein by heat exchange with the exhaust, and the evaporating working fluid and the heated working fluid in the heated fluid tank (31). The working fluid is cooled and condensed by heat exchange with the heating fluid. Both the condensing unit (50) for heating the fluid to be heated, the steam pipe (60) for flowing the working fluid evaporated in the evaporating unit (40) into the condensing unit (50), and the working fluid condensed in the condensing unit (50) And a reflux pipe (61) for refluxing the water to the evaporation section (40).

  Since the lead-out portion (33) of the heated fluid tank (31) is provided above the introduction portion (32), an upward flow occurs in the heated fluid in the heated fluid tank (31). Bubbles generated in the fluid are pushed out together with the flow of the heated fluid through the outlet portion (33) to the heated fluid circuit (21), and do not easily accumulate on the heated fluid tank (31). Therefore, since it is possible to prevent gas from accumulating at the upper part of the heated fluid tank (31), it is possible to prevent the condensation performance of the condensing unit (50) from being lowered and to improve the heat recovery performance of the exhaust heat recovery device. Moreover, since the heat capacity in the heated fluid tank (31) in a state where the flow of the heated fluid is stopped can be increased, the heated fluid is locally boiled in the heated fluid tank (31) during the dead soak. Can be prevented.

  The invention according to claim 2 is characterized in that the lead-out portion (34) is provided in the vicinity of the upper end of the side surface of the heated fluid tank (31).

  As a result, the bubbles generated in the heated fluid are easily pushed out to the heated fluid circuit (21) via the lead-out portion (34), and thus are less likely to accumulate in the upper portion of the heated fluid tank (31).

  The invention according to claim 3 is characterized in that the lead-out portion (35) is provided on the upper surface portion of the heated fluid tank (31).

  As a result, the bubbles generated in the heated fluid are easily pushed out to the heated fluid circuit (21) via the lead-out portion (35), so that the bubbles are more unlikely to accumulate in the upper portion of the heated fluid tank (31).

  In addition, the code | symbol in the bracket | parenthesis of each said means has shown an example of the corresponding relationship with the specific means as described in embodiment mentioned later.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram showing a schematic configuration of a cooling system and an exhaust system of a vehicle equipped with the exhaust heat recovery apparatus of the present embodiment. In FIG. 1, the flow direction of engine cooling water (heated fluid) is indicated by arrows. As shown in FIG. 1, the vehicle on which the exhaust heat recovery apparatus 1 is mounted includes a water-cooled engine (internal combustion engine) 10 as a driving source for traveling. An exhaust pipe 11 for discharging exhaust from the engine 10 to the outside is connected to the engine 10. In the middle of the exhaust pipe 11, a catalytic converter 12 for purifying the exhaust gas flowing through the exhaust pipe 11 is interposed. Further, a duct portion 13 of the exhaust heat recovery device 1 described later is provided on the downstream side of the catalytic converter 12 in the exhaust pipe 11.

  A radiator circuit 20, an exhaust heat recovery circuit (heated fluid circuit) 21, and a heater circuit 22 are connected to the engine 10. In the radiator circuit 20, the exhaust heat recovery circuit 21 and the heater circuit 22, engine coolant for cooling the engine 10 is circulated by, for example, an engine-driven water pump 23. For example, LLC is used as the engine cooling water.

  The radiator circuit 20 is provided with a radiator 24 that cools the engine coolant by heat exchange with outside air, and a bypass passage 25 that bypasses the radiator 24 and distributes the engine coolant. The flow rate of the engine cooling water passing through the radiator 24 and the flow rate of the engine cooling water passing through the bypass passage 25 are adjusted by a thermostat 26.

  The exhaust heat recovery circuit 21 branches from the radiator circuit 20 at the engine outlet and is joined to the radiator circuit 20 by the water pump 23. In the middle of the exhaust heat recovery circuit 21, a water tank (heated fluid tank) 31 of the exhaust heat recovery apparatus 1 described later is provided.

  The heater circuit 22 is a circuit that joins engine cooling water (hot water) flowing out from a portion different from the engine outlet of the radiator circuit 20 to the exhaust heat recovery circuit 21 on the downstream side of the exhaust heat recovery device 1. The heater circuit 22 is provided with a heater core 27 as a heating heat exchanger. The heater core 27 is disposed in an air conditioning case of an air conditioning unit (not shown), and heats conditioned air blown by a blower by heat exchange with engine cooling water.

  FIG. 2 is a cross-sectional view schematically showing the configuration of the exhaust heat recovery apparatus in the present embodiment. The vertical direction in FIG. 2 generally represents the vertical vertical direction. The thin solid arrow in FIG. 2 represents the flow direction of the working fluid in the liquid state, the broken arrow represents the flow direction of the working fluid in the gaseous state, and the thick arrow represents the flow direction of the engine coolant.

  As shown in FIG. 2, the exhaust heat recovery apparatus 1 has a loop heat pipe 2 that recovers exhaust heat discharged from the engine 10 and heats engine cooling water. The heat pipe 2 is provided with a sealing portion (not shown) that is used when the working fluid is sealed inside. The sealing part is sealed after the inside of the heat pipe 2 is decompressed and the working fluid is injected. As the working fluid, water, alcohol, fluorocarbon, chlorofluorocarbon (fluorocarbon) or the like is used.

  The heat pipe 2 has an evaporation section (heat absorption section) 40 that heats and evaporates the working fluid sealed inside by heat exchange with the exhaust. The evaporation part 40 is provided in the duct part 13 interposed in the middle of the exhaust pipe 11.

  For example, the evaporation unit 40 has a structure in which a plurality of flat tubes 41 extending in a substantially vertical direction and wave-like fins 42 thermally connected to the outer wall surface of each flat tube 41 are stacked in the horizontal direction. Yes. A flat container-like lower tank 43 is connected to the lower end of each flat tube 41. A flat container-like upper tank 44 is connected to the upper end of each flat tube 41. The lower tank 43 and the upper tank 44 are communicated with each other via the flat tubes 41.

  The heat pipe 2 has a condensing part (heat dissipating part) 50 that cools and condenses the working fluid and heats the engine cooling water by exchanging heat between the working fluid evaporated in the evaporation part 40 and the engine cooling water. Yes. The condensation unit 50 is interposed in the middle of the exhaust heat recovery circuit 21 and is accommodated in a water tank 31 disposed on the side of the duct unit 13.

  The condensing unit 50 has, for example, a structure in which a plurality of flat tubes 51 that extend substantially in the vertical direction and wavy fins 52 that are thermally connected to the outer wall surface of each flat tube 51 are stacked in the horizontal direction. Yes. A flat container-like lower tank 53 is connected to the lower end of each flat tube 51. A flat container-like upper tank 54 is connected to the upper end of each flat tube 51. The lower tank 53 and the upper tank 54 are communicated with each other via the flat tubes 51.

  An internal pressure operating valve 70 is provided in the lower tank 53 of the condensing unit 50. The inside of the internal pressure operating valve 70 is partitioned by a diaphragm 73 into an atmosphere side space 71 that communicates with the atmosphere side, and a communication channel 72 that communicates between the lower tank 53 and a reflux pipe 61 described later. The communication flow path 72 is provided with a valve body 74 that is connected to the diaphragm 73 and opens and closes the communication flow path 72.

  The diaphragm 73 is displaced in the left-right direction in FIG. 2 by the balance between the atmospheric pressure applied from the outside air side and the internal pressure of the heat pipe 2 (condensing unit 50). When the valve body 74 is displaced along with the displacement of the diaphragm 73, the communication channel 72 is opened and closed. Thus, the internal pressure operating valve 70 functions as a diaphragm type valve that opens and closes the communication flow path 72 according to the pressure of the working fluid. Specifically, when the internal pressure of the heat pipe 2 is less than a predetermined pressure (valve closing pressure), the communication flow path 72 is in an open state. When the internal pressure of the heat pipe 2 rises above a predetermined pressure and overcomes the atmospheric pressure, the valve body 74 is displaced rightward in FIG. 2 and the communication flow path 72 is closed.

  The upper tank 44 of the evaporation unit 40 and the upper tank 54 of the condensing unit 50 are communicated with each other by a steam pipe 60 that penetrates the duct unit 13 and the water tank 31. Further, the communication flow path 72 of the internal pressure operating valve 70 and a part of the flat tube 41 of the evaporation section 40 are communicated with each other by a reflux pipe 61 that penetrates the water tank 31 and the duct section 13. Accordingly, the lower tank 43, the flat tube 41, the upper tank 44, the steam pipe 60, the upper tank 54, the flat tube 51, the lower tank 53, the internal pressure operation valve 70 (communication flow path 72), the reflux pipe 61, the flat tube 41, and The lower tank 43 is connected in an annular shape and circulates the working fluid sealed inside.

  Below the side surface of the water tank 31 is provided an inlet pipe (introduction section) 32 for introducing engine cooling water flowing through the exhaust heat recovery circuit 21 into the water tank 31. In addition, an outlet pipe (leading part) 33 for leading the engine cooling water in the water tank 31 to the exhaust heat recovery circuit 21 is provided above the inlet pipe 32 on the side surface of the water tank 31.

  Each member constituting the heat pipe 2 is made of stainless steel having high corrosion resistance. After the members are assembled with each other, the members are integrally brazed with a brazing material provided at the contact portion or the fitting portion.

  Next, the operation of the exhaust heat recovery apparatus of this embodiment will be described.

  When the engine 10 is started, the water pump 23 is activated, and the engine coolant circulates through the radiator circuit 20, the exhaust heat recovery circuit 21, and the heater circuit 22. Exhaust gas from the engine 10 flows through the exhaust pipe 11, passes through the catalytic converter 12 and the duct portion 13 (evaporation portion 40) of the exhaust heat recovery device 1, and is discharged into the atmosphere. Further, the engine coolant circulating in the exhaust heat recovery circuit 21 passes through the water tank 31 (condenser 50) of the exhaust heat recovery device 1. The internal pressure of the heat pipe 2 is relatively low when the engine 10 is started, and gradually increases with the operation of the engine 10.

  In the evaporation part 40 of the heat pipe 2, the working fluid is heated and evaporated by heat exchange with the exhaust. The working fluid that has become vapor rises in the flat tube 41 and flows into the condenser 50 through the vapor pipe 60.

  On the other hand, the engine coolant flowing through the exhaust heat recovery circuit 21 flows into the water tank 31 via the inlet pipe 32. The engine cooling water that has flowed into the water tank 31 flows upward in the water tank 31 toward the outlet pipe 33.

  In the condensing unit 50, the working fluid is cooled and condensed by heat exchange between the working fluid evaporated in the evaporating unit 40 and the engine cooling water flowing in the water tank 31, and the engine cooling water is heated. When the internal pressure of the heat pipe 2 is less than the closing pressure of the internal pressure operating valve 70, the communication flow path 72 is in an open state, so that the condensed working fluid flows down through the flat tube 51, passes through the reflux pipe 61, and the evaporation section Return to 40. The heated engine cooling water flows out from the water tank 31 through the outlet pipe 33.

  As described above, the exhaust heat discharged from the engine 10 is transported from the evaporation unit 40 to the condensing unit 50 by the working fluid, and is released as condensation latent heat when the working fluid condenses in the condensing unit 50. As a result, the engine coolant flowing through the exhaust heat recovery circuit 21 is positively heated, so that warm-up of the engine 10 is promoted and the heating performance using the engine coolant is improved.

  When the internal pressure of the heat pipe 2 rises and becomes equal to or higher than the valve closing pressure, the diaphragm 73 and the valve body 74 of the internal pressure operating valve 70 are displaced rightward in FIG. 2 and the communication flow path 72 is closed. Thereby, the reflux of the working fluid condensed in the condensing unit 50 to the evaporation unit 40 is prevented. For this reason, when all the working fluid remaining in the evaporation section 40 evaporates, the recovery of the exhaust heat stops, and the condensed working fluid is stored on the condensing section 50 side. In this state, the internal pressure of the heat pipe 2 gradually decreases.

  When the internal pressure of the heat pipe 2 decreases and becomes equal to or lower than a predetermined valve opening pressure, the diaphragm 73 and the valve body 74 return to the left in FIG. 2, and the communication flow path 72 is opened again. Thereby, the return of the working fluid condensed in the condensing unit 50 to the evaporation unit 40 is resumed, and the recovery of the exhaust heat is resumed.

  In the present embodiment, the outlet pipe 33 of the water tank 31 is provided above the inlet pipe 32. For this reason, the engine cooling water in the water tank 31 flows upward of the water tank 31, passes through the upper part of the water tank 31, and flows out from the outlet pipe 33. Bubbles generated in the engine coolant due to mixing of gas such as air are directed upward due to the density difference from the engine coolant. However, since the bubbles are pushed out from the outlet pipe 33 together with the flow of the engine cooling water, it is difficult for the bubbles to accumulate in the upper part of the water tank 31.

  Therefore, according to the present embodiment, gas can be prevented from accumulating in the upper portion of the water tank 31, so that the condensation performance of the condensing unit 50 can be prevented from being lowered and the heat recovery performance of the exhaust heat recovery apparatus 1 can be improved.

  Moreover, according to this embodiment, since it can prevent that gas accumulates in the upper part of the water tank 31, the heat capacity in the water tank 31 in the state which stopped the flow of engine cooling water can be increased. Therefore, it is possible to prevent the engine cooling water from boiling locally in the water tank 31 during the dead soak.

  FIG. 3 is a cross-sectional view schematically showing a modification of the configuration in the vicinity of the condensing part of the exhaust heat recovery apparatus in the present embodiment. As shown in FIG. 3, in this modification, the outlet pipe 34 is provided in the vicinity of the upper end of the side surface of the water tank 31. Thereby, since air bubbles generated in the engine cooling water are further easily pushed out of the water tank 31 from the outlet pipe 34, it is possible to more reliably prevent gas from being accumulated in the upper portion of the water tank 31.

  FIG. 4 is a cross-sectional view schematically showing another modification of the configuration of the exhaust heat recovery apparatus in the present embodiment. As shown in FIG. 4, in this modification, the outlet pipe 35 is provided upward on the upper surface portion of the water tank 31. Thereby, since air bubbles generated in the engine cooling water are further easily pushed out of the water tank 31 from the outlet pipe 35, it is possible to more reliably prevent gas from being accumulated in the upper portion of the water tank 31.

(Other embodiments)
In the above-described embodiment, engine cooling water is used as the fluid to be heated. In addition, inverter cooling water, automatic transmission fluid (ATF), engine oil, or the like can also be used as the fluid to be heated.

It is a mimetic diagram showing a schematic structure of a cooling system and an exhaust system of a vehicle carrying an exhaust heat recovery device of a 1st embodiment. It is sectional drawing which shows typically the structure of the exhaust heat recovery apparatus in 1st Embodiment. It is sectional drawing which shows typically the modification of a structure of the exhaust heat recovery apparatus in 1st Embodiment. It is sectional drawing which shows typically the other modification of the structure of the exhaust-heat-heat recovery apparatus in 1st Embodiment. It is sectional drawing which shows typically the structure of a condensing part vicinity among the exhaust heat recovery apparatuses provided with the loop type heat pipe.

Explanation of symbols

1 exhaust heat recovery device 2 heat pipe 10 engine (internal combustion engine)
21 Exhaust heat recovery circuit (heated fluid circuit)
31 Water tank (heated fluid tank)
32 Inlet pipe (introduction part)
33, 34, 35 Outlet pipe (outlet)
40 Evaporating part 50 Condensing part 60 Steam pipe 61 Reflux pipe

Claims (3)

An exhaust heat recovery device that recovers exhaust heat of exhaust discharged from an internal combustion engine (10) to heat a heated fluid,
A heated fluid tank (31) interposed in a heated fluid circuit (21) for circulating the heated fluid;
An introduction portion (32) provided in the heated fluid tank (31), for introducing the heated fluid of the heated fluid circuit (21) into the heated fluid tank (31);
A lead-out portion that is provided above the introduction portion (32) of the heated fluid tank (31) and that leads the heated fluid in the heated fluid tank (31) to the heated fluid circuit (21). (33)
An evaporating section (40) for heating and evaporating the working fluid enclosed therein by heat exchange with the exhaust;
A condenser (50) for cooling and condensing the working fluid by heat exchange between the evaporated working fluid and the heated fluid in the heated fluid tank (31), and heating the heated fluid;
A steam pipe (60) for allowing the working fluid evaporated in the evaporator (40) to flow into the condenser (50);
An exhaust heat recovery apparatus comprising: a reflux pipe (61) for refluxing the working fluid condensed in the condenser (50) to the evaporator (40).   The exhaust heat recovery apparatus according to claim 1, wherein the lead-out portion (34) is provided in the vicinity of an upper end portion of a side surface of the heated fluid tank (31).   The exhaust heat recovery apparatus according to claim 1, wherein the lead-out portion (35) is provided on an upper surface portion of the heated fluid tank (31).

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