JP2007024423A - Exhaust heat recovery device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust heat recovery device capable of approximately equalizing exhaust heat recovery efficiency and dryout characteristics of a plurality of heat pipes arranged in the exhaust gas flowing direction. <P>SOLUTION: The plurality of heat pipes 13-15 for transporting exhaust heat of an exhaust gas to cooling water of a vehicle engine 1, respectively comprise heating portions arranged in several rows in the exhaust gas flowing direction in an exhaust pipe 3 in which the exhaust gas is circulated, and cooling portions 2a to which the refrigerant in the heat pipes evaporated by the heating portions 2c, is moved to be condensed by the cooling water flowing outside. Heat transfer fins 16, 17, 18 are mounted in the heating portions 2c, and areas of the fins of the most upstream heat pipe 13 is smaller than that in the most downstream heat pipe 15. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to an exhaust heat recovery apparatus that heats cooling water of an internal combustion engine by using exhaust heat of exhaust gas of the internal combustion engine using a heat pipe.

  Conventionally, as this kind of exhaust heat recovery device, among the heating part and cooling part of the heat pipe, the heating part is disposed in the exhaust pipe of the vehicle engine, and the cooling part is brought into thermal contact with the cooling water of the vehicle engine. Because exhaust heat of exhaust gas is transported to the cooling water of the vehicle engine and the cooling water is heated at low temperatures, the engine warm-up performance and the heating performance of the heater using the cooling water as a heating source are improved. An apparatus that can do this is known (see Non-Patent Document 1, for example).

Furthermore, in Non-Patent Document 1, by regulating the amount of working medium liquid enclosed in the heat pipe, even if the engine speed increases, dryout occurs in the heating unit and heat transport can be suppressed. It is described.
Wolf Dietrich Munzel, Daimler-Benz AG, “Heat Pipes for Recovery from Exhaust Gas of a Diesel Engineer in a Passenger Car” Proc. of International Heat Pipe Pipe Confence in Glenoble, France, 1987, PP. 740-743

  However, in the exhaust heat recovery apparatus described in Non-Patent Document 1, when exhaust heat recovery is performed using a plurality of heat pipes arranged in the exhaust gas flow direction, the heat disposed on the downstream side of the exhaust gas flow Since the temperature of the exhaust gas flowing around the pipe is lower than that of the upstream heat pipe, the temperature difference between the exhaust gas and the cooling water of the vehicle engine is small, and the exhaust heat recovery efficiency is low. It was. Moreover, since the temperature difference between the heating part and the cooling part of the heat pipe increases as the heat pipe is arranged on the upstream side of the exhaust gas flow, there is a problem that dryout (heat transport stop) is likely to occur.

  Accordingly, an object of the present invention has been made in view of the above problems, and the exhaust heat recovery efficiency and dry-out characteristics of a plurality of heat pipes arranged in the flow direction of the exhaust gas are made close to each other, and the exhaust heat recovery is performed. It is in providing the exhaust heat recovery apparatus excellent in.

  In order to achieve the above object, the following technical means are adopted. That is, according to the first aspect of the present invention, in order to transport exhaust heat of exhaust gas from the vehicle engine (1) to the cooling water of the vehicle engine (1), exhaust heat recovery is performed by a plurality of heat pipes (13 to 15). The exhaust heat recovery apparatus to perform, wherein the plurality of heat pipes (13 to 15) are arranged in a plurality of rows in the exhaust gas flow direction in the exhaust pipe (3) through which the exhaust gas flows. (2c) and a cooling unit (2a) in which the refrigerant in the heat pipe evaporates and moves in the heating unit (2c) and is condensed by the cooling water flowing outside, the heating unit (2c) ) In the exhaust heat recovery area in the most upstream heat exhaust area in the most downstream heat pipe (15) in which the exhaust gas flows through the periphery of the heating unit (2c). 13) Characterized by being configured to be smaller toward the exhaust heat recovery area definitive.

  According to the first aspect of the present invention, a plurality of heat pipes arranged in the flow direction of the exhaust gas, the exhaust heat recovery area of the heat pipe located on the upstream side is reduced, thereby the upstream heat pipe. As the exhaust heat recovery efficiency of the exhaust heat recovery device as a whole can be improved, the exhaust heat recovery efficiency and dryout characteristics of the heat pipes arranged in the flow direction can be made closer to each other by reducing the amount of exhaust heat absorption. it can.

  According to a second aspect of the present invention, in the exhaust heat recovery apparatus according to the first aspect, the heating part (2c) is provided with heat transfer fins (16, 17, 18), The area of the heat pipe (13) located on the most upstream side is smaller than that of the heat pipe (15) located on the most downstream side.

  According to the second aspect of the present invention, since the area of the fin located on the upstream side in the exhaust gas flow direction is configured to be smaller, the exhaust heat absorption amount of the upstream heat pipe can be reduced and the flow can be reduced. Since the exhaust heat recovery efficiency and the dry-out characteristics of the heat pipes arranged in the direction can be made close to each other, the exhaust heat recovery performance can be improved as a whole exhaust heat recovery apparatus.

  According to a third aspect of the present invention, in the exhaust heat recovery apparatus according to the first aspect, the lengths of the plurality of heat pipes (24 to 28) constituting the heating unit (30c) are located on the most downstream side. The heat pipe (24) located on the most upstream side is shorter than the heat pipe (28).

  According to the third aspect of the present invention, the length of the heat pipe located upstream in the exhaust gas flow direction is configured to be shorter, thereby reducing the amount of heat absorbed by the upstream heat pipe. Since the exhaust heat recovery efficiency and dry-out characteristics of the heat pipes arranged in the flow direction can be made close to each other, the exhaust heat recovery performance can be improved as a whole exhaust heat recovery apparatus.

  According to a fourth aspect of the present invention, in the exhaust heat recovery apparatus according to the first aspect, the refrigerant flow path cross-sectional area in the heat pipe (13-15) constituting the heating unit (40c) is the most downstream. The heat pipe (13) located on the most upstream side is made larger than the heat pipe (15) located.

  According to the fourth aspect of the present invention, the refrigerant flow passage cross-sectional area of the heat pipe located on the upstream side in the exhaust gas flow direction is configured to be larger than that of the downstream heat pipe, so that dryout is less likely to occur. The dry-out characteristics of a plurality of heat pipes arranged in the flow direction can be made closer to each other.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows a corresponding relationship with the specific means of embodiment mentioned later.

(First embodiment)
Below, 1st Embodiment is described using FIGS. 1-3. FIG. 1 is a schematic diagram showing the relationship between the exhaust heat recovery apparatus of this embodiment and a vehicle engine or the like. FIG. 2 is a schematic view showing another relationship between the exhaust heat recovery apparatus of the present embodiment and a vehicle engine or the like. FIG. 3 is a schematic diagram showing the configuration of the exhaust heat recovery apparatus in the present embodiment.

  The relationship between the vehicle engine 1 shown in FIG. 1, the exhaust heat recovery device 2, and other components will be described below. The vehicle engine 1 is a water-cooled internal combustion engine, a radiator circuit 8 that cools the vehicle engine 1 by circulating cooling water of the vehicle engine 1, and a heater that heats conditioned air using the cooling water as a heating source of hot water. 5 is connected. Further, the exhaust gas after the fuel combusts in the internal combustion engine passes through the exhaust pipe 3 communicating with the vehicle engine 1, and the exhaust heat recovery device 2 recovers the exhaust heat of the exhaust gas, and a catalytic converter (illustrated). Not purified) and discharged to the outdoors.

  The radiator circuit 8 is provided with the radiator 4, and the radiator 4 cools the cooling water circulating in the radiator circuit 8 by the water pump 6 by heat exchange with the outside air. Further, the radiator circuit 8 is provided with a bypass passage through which the cooling water flows around the radiator 4 so that the amount of cooling water flowing through the radiator 4 and the amount of cooling water flowing through the bypass passage are adjusted by the thermostat 7. It has become. In particular, during warm-up, the amount of cooling water on the bypass passage side increases and warm-up is promoted. That is, overcooling of the cooling water by the radiator 4 is prevented. In the radiator circuit 8, the pipes connected in the order of the vehicle engine 1, the radiator 4, the thermostat 7, and the water pump 6 have a larger pipe inner diameter than the pipes constituting the other circuits as shown in FIG. The cooling water will flow.

  In a circuit connecting the vehicle engine 1, the water pump 6, and the heater 5 as a heating heat exchanger, the water pump 6 circulates cooling water (hot water). The heater 5 is disposed in an air conditioning case (not shown) of the air conditioning unit, and heats the conditioned air blown by a blower (not shown) by heat exchange with cooling water (hot water).

  The exhaust heat recovery apparatus 2 has a heat pipe composed of a plurality of tubes, a heating part 2c on one side of each heat pipe is disposed in the exhaust pipe 3, and a cooling part 2a on the other side is provided with cooling water. It is arrange | positioned in the flow path. Each constituent member of the exhaust heat recovery apparatus 2 is made of a stainless material having high corrosion resistance. After the constituent members are assembled, they are integrally brazed and joined by a brazing material provided at the contact portion or the fitting portion. ing.

  The way in which the cooling water flows varies depending on the temperature. When the coolant temperature is relatively low, such as immediately after the start of the vehicle engine 1, the thermostat 7 is closed. Therefore, the coolant that has flowed out of the vehicle engine 1 due to the suction of the water pump 6 passes through the heater 5 and passes through the water pump 6. Return to the vehicle engine 1 via. At the same time, the cooling water flowing out from the vehicle engine 1 returns to the vehicle engine 1 through the water pump 6 without flowing into the heater 5 through the cooling part 2a of the exhaust heat recovery device 2 due to the suction of the water pump 6.

  On the other hand, when the cooling water temperature becomes relatively high, the thermostat 7 is opened, and the cooling water flowing out of the vehicle engine 1 by the suction of the water pump 6 mainly flows into the radiator 4 and is cooled and passes through the water pump 6. To return to the vehicle engine 1. At the same time, the amount of cooling water flowing to the radiator 4 is not as large as the amount of cooling water flowing through the radiator 4, but by the suction of the water pump 6, the flow of cooling water returning to the vehicle engine 1 via the exhaust heat recovery device 2 and the heater 5 Then, a flow of cooling water returning to the vehicle engine 1 is generated. The thermostat 7 is configured to open the flow path when the water temperature exceeds a predetermined temperature. For example, the thermostat 7 is configured to open the flow path when the water temperature exceeds 80 ° C. and fully open at 85 ° C. or higher.

  Moreover, the other example showing the relationship between the exhaust heat recovery apparatus 2, the vehicle engine 1, etc. is demonstrated using FIG. The cooling water path shown in FIG. 2 is the same as the cooling water path shown in FIG. 1 described above. The cooling water flowing out of the vehicle engine 1 by the suction of the water pump 6 passes through the cooling section 2a of the exhaust heat recovery device 2. After passing, the cooling water flowing out from the vehicle engine 1 due to the suction of the water pump 6 passes through the cooling unit 2a of the exhaust heat recovery device 2 because it does not have a path to return to the vehicle engine 1 without passing through the heater 5. After that, the difference is that a circuit 9 via a heater is provided to return to the vehicle engine 1 via the heater 5. The other components with the same reference numerals shown in FIG. 2 are the same as those shown in FIG.

  Hereinafter, the configuration of the exhaust heat recovery apparatus 2 will be described with reference to FIG. Each tube constituting the exhaust heat recovery device 2 is evacuated so that the inside is in a vacuum state, and then a predetermined amount of refrigerant as a working medium is sealed and operates as a heat pipe. When water is used as the refrigerant as the working medium, the boiling point of water is normally 100 ° C. at 1 atm. However, since the heat pipe is evacuated, the boiling point of the enclosed water is 30 It is as low as ˜40 ° C. As the working medium, alcohol, fluorocarbon, chlorofluorocarbon or the like can be used in addition to water.

  Each heat pipe is used in a posture in which the longitudinal direction is the vertical direction, and includes a heating unit 2c on the lower side, a cooling unit 2a on the upper side, and a heat insulating unit 2b between the heating unit 2c and the cooling unit 2a. The so-called bottom heat type is used. Further, the inner wall of the tube corresponding to the cooling part 2a is provided with a wick (porous material) made of a metal mesh, a metal felt, a sintered metal or the like, thereby increasing the amount of heat transport. The heat pipe is a closed-loop heat transfer element that uses latent heat generated by evaporation and condensation of the refrigerant as the working fluid sealed inside, and can transfer a large amount of heat with a small temperature difference. The refrigerant sealed inside the heating part 2c of each heat pipe evaporates due to exhaust heat of the exhaust gas applied to the outside of the heating part 2c, becomes steam and moves to the cooling part 2a side through the heat insulating part 2b. The cooling unit 2a cools and condenses with cooling water flowing outside. Simultaneously with this condensation, the refrigerant transports the exhaust heat of the exhaust gas received during evaporation to the cooling water to heat the cooling water, and this transported heat is used to warm up the vehicle engine 1 and in the winter season. It will be used as heating energy at the start-up.

  The heat pipes 13, 14, and 15 have a cylindrical shape in which the periphery of the heating unit 2 c is surrounded by a side plate 23 or the like having a substantially rectangular outer shape, and an inflow port 19 and an outflow port 20 that open the exhaust gas flow direction are formed. It arrange | positions in order from the upstream of the flow direction of exhaust gas in the box. The cylindrical box surrounding the heating unit 2 c is connected to the exhaust pipe 3 via an upstream flange 21 formed around the inlet 19 and a downstream flange 22 formed around the outlet 20. Has been. By connecting to the exhaust pipe 3, the inside of the cylindrical box body constitutes an exhaust gas circulation duct having a substantially rectangular cross section.

  Each heat pipe is a cylindrical body, and one end side communicates with a refrigerant replenishing port (not shown) for filling the refrigerant, and the other end side is closed. The heat pipes that are heat-evaporated in the heating part 2c by adopting a configuration in which the heat-insulating part 2b of each heat pipe is formed above the cylindrical box surrounding the heating part 2c and the surface and surroundings of the heat pipe are insulated. The refrigerant inside is prevented from condensing. On the upper side of the heat insulating part 2b, a cooling part 2a of a heat pipe is formed, and a flat box-shaped tank 10 that completely surrounds the cooling part 2a is provided so as to be isolated from the surface of the heat insulating part 2b of the heat pipe. Yes. The tank 10 is provided with a cooling water inlet 11 and a cooling water outlet 12 to which pipes communicating with the vehicle engine 1 shown in FIGS. 1 and 2 are connected. And the cooling water which flowed out from the vehicle engine 1 by the suction of the water pump 6 flows through the piping, flows in from the cooling water inlet 11, and flows through the cooling portion 2 a of the heat pipe disposed inside the tank 10. The condensed latent heat is received and warmed, flows out from the cooling water outlet 12, and returns to the vehicle engine 1 again through the water pump 6. Further, the heat pipes are arranged in a plurality of rows in the depth direction of FIG. 3 in a direction perpendicular to the exhaust gas flow direction.

  Each heat pipe is provided with a heat transfer fin in the heating section 2c, and the area of this fin is the heat pipe 13 located most upstream than the heat pipe 15 located most downstream in the flow direction of the exhaust gas. The area at is smaller. That is, the exhaust heat recovery area in the heat pipe 13 located on the most upstream side is made smaller than the exhaust heat recovery area on the heat pipe 15 located on the most downstream side where the exhaust gas flows through the periphery of the heating unit 2c. It constitutes.

  Preferably, the heat pipe located upstream in the exhaust gas flow direction receives more exhaust heat of the exhaust gas, so that the heat pipe located in the upstream position in the order of the heat pipes 13, 14 and 15 recovers exhaust heat. It is preferable that the fin area corresponding to the area be reduced. The fins are provided so as to be penetrated by the heat pipes. The fins 16 are coupled to the heat pipes 13 so as to surround the periphery of the heat pipes. The fin 16, the fin 17, and the fin 18 are coupled to the heat pipe 15 so as to surround the periphery of the heat pipe 15. In other words, the fins 18, the fins 17, and the fins 16 are sequentially arranged at predetermined intervals from the upper part of the heating unit 40c to the lower side, and the arrangement in this order reaches the lower end part from the upper end part of the heating part 2c. The heat pipes and fins are combined in such a manner that each heat pipe in the heating unit 40c penetrates all of these fins. Further, the arrangement of the fins 16, 17, and 18 is similar to the horizontal direction of FIG. 3 for the heat pipes arranged in a plurality of rows in the depth direction of FIG. 3. The area of the heat pipe 13 located on the most upstream side is smaller than the heat pipe 15 located on the most downstream side.

  The operation of the exhaust heat recovery apparatus 2 based on the above configuration will be described. When the vehicle engine 1 is operated, the water pump 6 is operated together with this, and the cooling water circulates through the radiator circuit 8, the heater circuit 9, and the like. The cooling water circulating through the heater circuit 9 and the like circulates around the cooling unit 2a of the exhaust heat recovery device 2. Further, the exhaust gas of the fuel combusted in the vehicle engine 1 passes through the exhaust pipe 3, passes through the periphery of the heating unit 2 c of the exhaust heat recovery device 2, and is further discharged into the atmosphere through the exhaust pipe.

  In the exhaust heat recovery device 2, the refrigerant in each heat pipe receives heat from the exhaust gas flowing in the cylindrical box body communicating with the exhaust pipe 3 in the heating unit 2c, evaporates to the vapor, and becomes a heat pipe. The inside rises and flows into the cooling part 2a. The steam that has flowed into the cooling unit 2a is cooled by the cooling water flowing through the tank 10, becomes condensed water by the wick provided on the inner wall, descends due to gravity, and returns to the heating unit 2c.

  In this way, the heat of the exhaust gas is transmitted to the refrigerant and transported from the heating unit 2c to the cooling unit 2a, and when the vapor condenses in the cooling unit 2a, it is released as condensation latent heat, and the cooling water flowing in the tank 10 is It will be heated. In addition, in the exhaust heat of exhaust gas, there exists a part which is moved to the cooling part 2a from the heating part 2c by heat conduction through the wall surface of each heat pipe.

  With the amount of exhaust heat that increases in accordance with the load of the vehicle engine 1, the amount of heat that is transported from the heating unit 2c to the cooling unit 2a, that is, the amount of heat transfer to the cooling water, increases up to a predetermined load. The above is called ON of the exhaust heat recovery switch by the heat pipe.

  As described above, when the vehicle engine 1 is started when the outside air temperature is relatively low, the exhaust heat recovery switch by the heat pipe is turned on, the cooling water is positively heated, and the warm-up of the vehicle engine 1 is promoted. Therefore, reduction of friction loss of the vehicle engine 1 and suppression of fuel increase for improving low temperature startability can be achieved and fuel efficiency can be improved. Moreover, the heating performance of the heater 5 which uses cooling water as a heat source can also be improved.

  On the other hand, when the load of the vehicle engine 1 increases from the predetermined load and the exhaust heat quantity further increases, the evaporation of water in the heating unit 2c is promoted, and the steam flow rate toward the cooling unit 2a, that is, upward, increases. become. At this time, the increase in the steam flow rate prevents the condensed water condensed in the cooling unit 2a from being lowered, and the condensed water remains retained by the wick. Then, the water in the heating unit 2c is completely evaporated and dryout occurs, and heat transport due to water evaporation and condensation is stopped. In such a situation, the amount of heat transmitted to the cooling water side is only heat conduction through the heat pipe. This is referred to as turning off the exhaust heat recovery switch using a heat pipe. Note that switching the exhaust heat recovery switch by the heat pipe to ON or OFF corresponds to the heat switch function.

  Therefore, if exhaust heat recovery continues as the exhaust heat amount increases as the load of the vehicle engine 1 increases, the temperature of the cooling water rises too much and exceeds the heat dissipation capability of the radiator 4, leading to overheating. End up. This can be prevented by switching the aforementioned exhaust heat recovery switch to OFF. As described above, the exhaust heat recovery apparatus according to the present embodiment is configured so that the heat pipes 13 to 15 have exhaust gas through which the exhaust gas circulates in order to transport the exhaust heat of the exhaust gas from the vehicle engine 1 to the cooling water of the vehicle engine 1. A heating unit 2c arranged in a plurality of rows in the flow direction of the exhaust gas in the pipe 3, and a cooling unit 2a in which the refrigerant in the heat pipe evaporates and moves in the heating unit 2c and is condensed by the cooling water flowing outside. The exhaust heat recovery area in the heating unit 2c is equal to the exhaust heat recovery area in the heat pipe 13 located most upstream than the exhaust heat recovery area in the heat pipe 15 located most downstream where the exhaust gas flows. It is configured to be smaller. According to this configuration, the amount of exhaust heat absorbed by the heat pipe on the upstream side can be reduced, so that the ambient temperature of the heat pipe is lowered and the heat recovery efficiency is lowered as it becomes downstream in the exhaust gas flow direction. The exhaust heat recovery efficiency of the heat pipes arranged in the flow direction can be made close to each other. In addition, according to this configuration, the phenomenon that the heat temperature of the heating pipe and the cooling section of the heat pipe is sequentially dried out from the heat pipe on the upstream side due to a large upstream temperature in the exhaust gas flow direction is prevented. And the dry-out characteristics of a plurality of heat pipes arranged in the flow direction can be made closer to each other.

  Moreover, the heat transfer fins 16, 17, and 18 are provided in the heating unit 2 c, and the area of these fins is smaller in the area of the heat pipe 13 that is located most upstream than the heat pipe 15 that is located most downstream. It is configured to do. When this configuration is adopted, the exhaust heat absorption amount of the upstream heat pipe can be reduced, and the exhaust heat recovery efficiency and the dry-out characteristics of the heat pipes arranged in the flow direction can be made close to each other.

(Second Embodiment)
In the present embodiment, the configuration of the exhaust heat recovery apparatus different from the first embodiment will be described with reference to FIG. Further, the configuration of the exhaust heat recovery apparatus 30 shown in the present embodiment does not include the length relationship of each heat pipe and the fins for heat transfer as compared with the exhaust heat recovery apparatus shown in FIG. 3 described above. However, the description of the relationship between the exhaust heat recovery device 30 and the vehicle engine 1, the cooling water path, and the operation of the exhaust heat recovery device 30 is the same as in the first embodiment, and is left to the first embodiment. It is omitted here. FIG. 4 is a schematic diagram showing the configuration of the exhaust heat recovery apparatus in the present embodiment.

  As shown in FIG. 4, each heat pipe constituting the exhaust heat recovery apparatus 30 is used in a posture in which the longitudinal direction is the vertical direction, the heating unit 30 c on the lower side, the cooling unit 30 a on the upper side, and the heating unit. It is configured as a so-called bottom heat type having a heat insulating part 30b between 30c and the cooling part 30a. The heat pipes 24, 25, 26, 27, and 28 have an inlet 29 and an outlet 31 that surround the periphery of the heating unit 30 c with a side plate 35 having an outer shape that is substantially trapezoidal and that opens the flow direction of the exhaust gas. In the formed cylindrical box body, it arrange | positions in order toward the downstream from the upstream of the flow direction of exhaust gas. The lengths of the heat pipes 24 to 28 are configured such that the heat pipe 24 located on the most upstream side is shorter than the heat pipe 28 located on the most downstream side in the exhaust gas flow direction. Preferably, the heat pipe located upstream in the exhaust gas flow direction receives more exhaust heat of the exhaust gas, and therefore the heat pipe present in the upstream position in the order of the heat pipes 24, 25, 26, 27, 28. It is preferable that the length is shortened. The cylindrical box surrounding the heating unit 30 c is connected to the exhaust pipe 3 via an upstream flange 32 formed around the inlet 29 and a downstream flange 33 formed around the outlet 31. Has been. By connecting to the exhaust pipe 3, the inside of the cylindrical box body constitutes an exhaust gas circulation duct having a substantially rectangular cross section.

  A heat insulating part 30b of each heat pipe is formed above the cylindrical box surrounding the heating part 30c of each heat pipe, and a cooling part 30a of the heat pipe is formed above the heat insulating part 30b. A flat box-shaped tank 34 that completely surrounds the cooling unit 30a is provided so as to be isolated from the surface of the heat insulating unit 30b of the heat pipe. The tank 34 is provided with a cooling water inlet 11 and a cooling water outlet 12 to which pipes communicating with the vehicle engine 1 shown in FIGS. 1 and 2 are connected. And the cooling water which flowed out of the vehicle engine 1 by the suction of the water pump 6 flows into the cooling water inflow port 11 through the piping, and the refrigerant flows through the cooling portion 30a of the heat pipe disposed inside the tank 34. The condensed latent heat is received and warmed, flows out from the cooling water outlet 12, and returns to the vehicle engine 1 again through the water pump 6. Further, the heat pipes are arranged in a plurality of rows in the depth direction of FIG. 4 in a direction perpendicular to the exhaust gas flow direction. As described above, according to the exhaust heat recovery apparatus of the present embodiment, the lengths of the plurality of heat pipes 24 to 28 constituting the heating unit 2c are the longest than the heat pipe 28 located most downstream in the exhaust gas flow direction. The heat pipe 24 located upstream is made shorter. When this configuration is adopted, the amount of exhaust heat absorbed by the upstream heat pipe can be reduced, so that the ambient temperature of the heat pipe decreases as the exhaust gas flows downstream, and the heat recovery efficiency decreases. Therefore, the exhaust heat recovery efficiency and the dry-out characteristics of the plurality of heat pipes arranged in the flow direction are made close to each other, and an exhaust heat recovery apparatus with excellent performance can be obtained.

(Third embodiment)
In the present embodiment, the configuration of the exhaust heat recovery apparatus different from the first and second embodiments will be described with reference to FIGS. 5 and 6. In addition, the configuration of the exhaust heat recovery device 40 shown in the present embodiment is compared with the above-described exhaust heat recovery device shown in FIG. Although the configuration is different, the description of the relationship between the exhaust heat recovery device 40 and the vehicle engine 1, the cooling water path, and the operation of the exhaust heat recovery device 40 is the same as in the first embodiment, and is left to the first embodiment. This is omitted here. FIG. 5 is a schematic diagram showing the configuration of the exhaust heat recovery apparatus in the present embodiment, and FIG. 6 is a cross-sectional view showing the configuration of the heat pipe in the exhaust heat recovery apparatus.

  As shown in FIG. 5, each heat pipe having a flat cross section constituting the exhaust heat recovery device 40 is used in a posture in which the longitudinal direction is the vertical direction, the heating unit 40 c on the lower side, and the cooling unit on the upper side. 40a and a so-called bottom heat type in which a heat insulating part 40b is provided between the heating part 40c and the cooling part 40a.

  The heat pipes 13, 14, and 15 have a cylindrical shape in which the periphery of the heating unit 40 c is surrounded by a side plate 37 or the like having a substantially rectangular outer shape, and an inflow port 19 and an outflow port 20 that open the exhaust gas flow direction are formed. It arrange | positions in order from the upstream of the flow direction of exhaust gas in the box. The cylindrical box surrounding the heating unit 40 c is connected to the exhaust pipe 3 via an upstream flange 21 formed around the inlet 19 and a downstream flange 22 formed around the outlet 20. Has been. By connecting to the exhaust pipe 3, the inside of the cylindrical box body constitutes an exhaust gas circulation duct having a substantially rectangular cross section.

  Above this heat insulating part 40b, a cooling part 40a of a heat pipe is formed, and a flat box-like tank 10 that completely surrounds the cooling part 40a is provided so as to be isolated from the surface of the heat insulating part 40b. The tank 10 is provided with a cooling water inlet 11 and a cooling water outlet 12 to which pipes communicating with the vehicle engine 1 shown in FIGS. 1 and 2 are connected. And the cooling water which flowed out of the vehicle engine 1 by the suction of the water pump 6 flows in from the cooling water inflow port 11 through the piping, and the refrigerant flows through the cooling portion 40a of the heat pipe disposed inside the tank 10. The condensed latent heat is received and warmed, flows out from the cooling water outlet 12, and returns to the vehicle engine 1 again through the water pump 6. Further, the heat pipes are arranged in a plurality of rows in the depth direction of FIG. 5 in a direction perpendicular to the exhaust gas flow direction.

  Each heat pipe is provided with a heat transfer fin 36 in the heating portion 40c, and the fins 36 are similarly connected so as to surround the periphery of the heat pipe in any of the heat pipes 13, 14, and 15. . In other words, a plurality of fins 36 are arranged at predetermined intervals in the vertical direction of the heating unit 40c, and each heat pipe in the heating unit 40c is connected to each heat pipe in a form that penetrates all of the fins 36. Fins 36 are joined. Further, the fins 36 are also provided in the same manner as the horizontal direction of FIG. 5 for the heat pipes arranged in a plurality of rows in the depth direction of FIG. As shown in FIG. 6, the refrigerant flow passage cross-sectional area partitioned inside the heat pipes 13 to 15 arranged in the exhaust gas flow direction is located most upstream than the heat pipe 15 located most downstream of the exhaust gas flow. It is set as the structure which enlarges the direction of the heat pipe 13 to perform. Preferably, the heat pipe positioned upstream in the exhaust gas flow direction receives more exhaust heat of the exhaust gas, and therefore the refrigerant vapor flow rate increases, so the heat pipes 13, 14, and 15 exist in the upstream position in this order. It is preferable that the heat pipe to be configured has a larger refrigerant flow path cross-sectional area. The adjustment of the cross-sectional area of the refrigerant flow path of the heat pipe utilizes the fact that the number of flow path divisions is increased by providing fins and partition plates in the pipe. For example, for the heat pipe 13 located on the most upstream side, two partition plates are provided in the pipe in parallel with the longitudinal direction of the pipe, and for the heat pipe 15 located on the most downstream side, four partition plates are provided in the pipe. Is provided in parallel with the longitudinal direction of the tube, and the heat pipe 14 positioned between the heat pipes 13 and 15 is configured such that three partition plates are provided in the tube in parallel with the longitudinal direction of the tube.

  As described above, according to the exhaust heat recovery apparatus of the present embodiment, the refrigerant flow path cross-sectional area in the heat pipes 13 to 15 constituting the heating unit 40c is the most than the heat pipe 15 located most downstream in the exhaust gas flow. The heat pipe 13 located upstream is configured to be larger. When this configuration is adopted, the flow rate of the refrigerant vapor that hinders the recirculation of the liquid flow in the heat pipe is inversely proportional to the cross-sectional area of the refrigerant flow path of the heat pipe. By designing to reduce the refrigerant vapor flow velocity inside, it is possible to bring the dry-out characteristics of a plurality of heat pipes arranged in the flow direction close to each other, so that the exhaust heat recovery device having excellent performance Will be obtained.

It is the schematic diagram which showed the relationship between the waste heat recovery apparatus of 1st Embodiment, a vehicle engine, etc. FIG. It is the schematic diagram which showed the other relationship between the waste heat recovery apparatus of 1st Embodiment, a vehicle engine, etc. FIG. It is the schematic diagram which showed the structure of the waste heat recovery apparatus in 1st Embodiment. It is the schematic diagram which showed the structure of the waste heat recovery apparatus in 2nd Embodiment. It is the schematic diagram which showed the structure of the waste heat recovery apparatus in 3rd Embodiment. It is sectional drawing which showed the pipe internal structure of the heat pipe in the waste heat recovery apparatus of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle engine 2, 30, 40 Waste heat recovery apparatus 2a Cooling part 2b Heat insulation part 2c Heating part 3 Exhaust pipe 13-15 Heat pipe 16-18 Fin 24-28 Heat pipe

Claims (4)

An exhaust heat recovery device for recovering exhaust heat by a plurality of heat pipes (13 to 15) for transporting exhaust heat of exhaust gas from the vehicle engine (1) to cooling water of the vehicle engine (1),
The plurality of heat pipes (13 to 15) include a heating unit (2c) arranged in a plurality of rows in a flow direction of the exhaust gas in an exhaust pipe (3) through which the exhaust gas flows.
The refrigerant in the heat pipe is vaporized and moved in the heating unit (2c), and is provided with a cooling unit (2a) that is condensed by the cooling water flowing outside,
The exhaust heat recovery area in the heating part (2c) is most upstream than the exhaust heat recovery area in the heat pipe (15) located on the most downstream side where the exhaust gas flows through the periphery of the heating part (2c). An exhaust heat recovery apparatus, characterized in that the exhaust heat recovery area in the heat pipe (13) positioned is smaller.   The heating part (2c) is provided with heat transfer fins (16, 17, 18), and the area of the fins is the heat pipe (15) located upstream from the heat pipe (15) located most downstream. 13. The exhaust heat recovery apparatus according to claim 1, wherein the area in 13) is smaller.   The length of the plurality of heat pipes (24 to 28) constituting the heating unit (30c) is greater in the heat pipe (24) located on the most upstream side than the heat pipe (28) located on the most downstream side. The exhaust heat recovery apparatus according to claim 1, wherein the exhaust heat recovery apparatus is shortened.   The refrigerant flow path cross-sectional area in the heat pipe (13-15) which comprises the said heating part (40c) is the said heat pipe (13) located in the most upstream rather than the heat pipe (15) located in the most downstream. The exhaust heat recovery apparatus according to claim 1, wherein the exhaust heat recovery apparatus is made larger.

Images