JP2007238026A - Exhaust system heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust system heat exchanger capable of preventing a circulation liquid from being overheated. <P>SOLUTION: An exhaust heat collection system 10 comprises a heat exchanger 18 for collecting the exhaust heat to perform the heat exchange between an exhaust gas of an internal combustion engine 12 and an engine cooling water for circulating the internal combustion engine 12, a cooling water circulation passage 30 for circulating the engine cooling water to the engine 12 and the heat exchanger 18 for collecting the exhaust heat, and an endothermic unit 32 for absorbing the heat from the engine cooling water when the temperature of the engine cooling water is not lower than a predetermined value. The endothermic unit 32 is provided in the cooling water circulation passage 30. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust system heat exchange device for exchanging heat between exhaust gas of an internal combustion engine and the circulating fluid of the internal combustion engine.

2. Description of the Related Art An exhaust heat utilization device for an internal combustion engine in which an exhaust gas of an internal combustion engine, a lubricating oil of the engine, and a heat storage material are disposed in an exhaust system of an automobile is known (for example, Patent Document 1). reference). In this technique, exhaust gas bypasses the heat exchanger after the engine is sufficiently warmed up to protect the heat exchanger from overheating.
Japanese Unexamined Patent Publication No. 7-119455

  However, in the conventional technology as described above, there is a restriction such as providing a bypass path for bypassing the heat exchanger, and in the case of a failure to switch to bypass, the exhaust gas exceeding the heat storage capacity of the heat storage material is used. There is a concern that the lubricating oil and the heat storage material may be overheated by heat input.

  In view of the above fact, an object of the present invention is to obtain an exhaust heat exchanger that can prevent the circulating fluid from overheating.

  An exhaust system heat exchanging device according to claim 1 is a heat exchanger for exchanging heat between exhaust gas of an internal combustion engine and circulating fluid circulating through the internal combustion engine, the internal combustion engine, and the heat exchange. And a heat absorption part that is provided in a liquid circulation path for circulating the circulating liquid in the vessel and absorbs heat from the circulating liquid when the temperature of the circulating liquid is equal to or higher than a predetermined temperature.

  In the exhaust system heat exchanging device according to claim 1, for example, by exchanging heat between the circulating fluid (low temperature fluid) such as lubricating oil and cooling water and the exhaust gas (high temperature fluid), the exhaust heat is recovered into the circulating fluid, Further, for example, the exhaust gas can be cooled. Here, since the heat absorption part is provided in the liquid circulation path that circulates the circulating fluid between the internal combustion engine and the heat exchanger (low temperature side thereof), when the temperature of the circulating fluid exceeds a predetermined temperature, the heat of the circulating fluid is increased. Is absorbed by the heat absorption part at a portion (liquid circulation path) where heat exchange with the exhaust gas is not performed. Thereby, the heat absorption part can effectively take heat from the circulating fluid without deteriorating due to the heat of the exhaust gas, for example.

  Thus, in the exhaust system heat exchange device according to the first aspect, overheating of the circulating fluid can be prevented. As the heat absorption part that absorbs heat at a predetermined temperature or higher, for example, a heat storage material that takes away latent heat due to phase transition, a heat storage material that takes away reaction heat by an endothermic reaction (for example, dehydration reaction), or the like can be used.

  The exhaust heat exchanger according to claim 2 is the exhaust heat exchanger according to claim 1, wherein the heat absorption part includes a latent heat storage material that absorbs heat from the circulating liquid by phase transition. The phase transition temperature is set below the boiling point of the circulating liquid.

  In the exhaust system heat exchange device according to claim 2, the latent heat storage material constituting the heat absorption part undergoes a phase transition from a solid phase to a liquid phase, for example, and a phase transition from a crystalline phase to an amorphous phase, for example, The latent heat required for the phase transition is taken from the circulating fluid, and boiling due to overheating of the circulating fluid is prevented. Further, the latent heat storage material (heat storage material) can be easily placed in a liquid circulation path by being enclosed in, for example, a microcapsule.

  The exhaust system heat exchange device according to a third aspect of the present invention is the exhaust system heat exchange device according to the first or second aspect, wherein the heat absorption part is connected to the internal combustion engine from the heat exchanger in the liquid circulation path. Toward the portion where the circulating fluid flows.

  In the exhaust heat exchanger according to claim 3, since the heat absorption part is provided at least in the part of the liquid circulation path where the circulating fluid flows from the heat exchanger toward the internal combustion engine, the heat absorption part is raised by the exhaust gas. Heat is absorbed from the high-temperature circulating liquid that has been heated (heated) and discharged from the heat exchanger. For this reason, overheating of the circulating fluid can be more effectively prevented.

  An exhaust system heat exchange device according to a fourth aspect of the present invention is the exhaust system heat exchange device according to any one of the first to third aspects, wherein the circulating fluid is for cooling the internal combustion engine. It is an engine coolant, and the fluid circulation path circulates the internal combustion engine, the heat exchanger, and a radiator through the engine coolant.

  In the exhaust heat exchanger according to the fourth aspect, the engine coolant normally cools the internal combustion engine while circulating through the internal combustion engine, the heat exchanger, and the radiator through the liquid circulation path. When the engine coolant temperature becomes equal to or higher than a predetermined temperature, the heat of the engine coolant is absorbed by the heat absorbing portion, and overheating of the engine coolant having a relatively low boiling point is prevented. As a result, even when the amount of heat supplied to the engine cooling water by the engine and the heat exchanger exceeds (temporarily exceeds) the capacity of the radiator, this excess heat can be absorbed by the heat absorption part.

  As described above, the exhaust system heat exchange device according to the present invention has an excellent effect that the circulating fluid can be prevented from being overheated.

  An exhaust heat recovery system 10 as an exhaust system heat exchange device according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 3.

  FIG. 1 shows a schematic overall flow diagram of the exhaust heat recovery system 10 in a schematic flow diagram. As shown in this figure, an exhaust heat recovery system 10 recovers heat of an exhaust gas of an internal combustion engine 12 of an automobile by heat exchange with engine cooling water as a circulating fluid (engine coolant) for heating and engines. 12 is an apparatus used for promoting warm-up.

  The engine 12 is connected to an exhaust pipe 14 that constitutes an exhaust system path for leading exhaust gas. On the exhaust gas discharge path by the exhaust pipe 14, a catalytic converter 16, an exhaust heat recovery heat exchanger 18, and a main muffler 20 are arranged in this order from the upstream side in the exhaust gas flow direction. The catalytic converter 16 is configured to purify exhaust gas passing therethrough by a built-in catalyst 16A. The main muffler 20 as a silencer is configured to reduce the exhaust noise generated when exhaust gas is discharged into the atmosphere.

  The exhaust heat recovery heat exchanger 18 as a heat exchanger is configured to recover the heat of the exhaust gas to the engine coolant by heat exchange between the engine coolant for cooling the engine 12 and the exhaust gas. . FIG. 1 shows an example of a heat exchanger 18 for exhaust heat recovery, which is a jacket type heat exchanger in which a heat exchange flow path 22A of engine cooling water is formed by a shell 22 provided around the exhaust pipe 14. However, instead of this, various types of heat exchangers can be employed.

  The shell 22 is provided with an inlet nozzle 24 for introducing engine cooling water and an outlet nozzle 26 for discharging engine cooling water. The inlet nozzle 24 and the outlet nozzle 26 are connected in series to the cooling water circulation path 30 for circulating the engine cooling water to the engine 12, the exhaust heat recovery heat exchanger 18, the radiator 28, and the heater core (not shown). Has been. As a result, the exhaust heat recovery system 10 is configured to generate a circulating flow of engine cooling water in the direction indicated by the arrow A in FIG.

  And in the exhaust heat recovery system 10, the heat absorption part 32 is provided in the cooling water circulation path 30 through which engine cooling water circulates. In this embodiment, the heat exchanger outlet flow path 30A from the exhaust heat recovery heat exchanger 18 (exit nozzle 26) to the engine 12 in the cooling water circulation path 30 and the exhaust heat recovery heat exchanger 18 (inlet) from the engine 12 are shown. A heat absorbing portion 32 is provided in a portion including the heat exchanger inlet channel 30B up to the nozzle 24).

  As shown in FIG. 2, the heat absorption part 32 has a coating (covering material) 36 covering an aluminum pipe 34 whose inside is a cooling water circulation path 30 (heat exchanger outlet flow path 30 </ b> A, heat exchanger inlet flow path 30 </ b> B). In addition, a large number of minute heat storage members 38 are dispersedly held. Each of the large number of heat storage bodies 38 is configured as a microcapsule in which the latent heat storage material 40 is enclosed (encapsulated) by the peripheral wall 42.

  As the latent heat storage material 40, for example, an inorganic substance such as sodium sulfate hydrate can be used, and the latent heat required for the phase transition from the solid phase to the liquid phase is absorbed from the engine coolant that is a heat source (latent heat is stored). It has become. In this embodiment, the phase transition temperature (melting point) from the solid phase to the liquid phase of the latent heat storage material 40 is set to 80 ° C. to 100 ° C., which is lower than the boiling point of the engine cooling water (approximately 110 ° C. to 120 ° C.). (The material of the latent heat storage material 40 is selected). The peripheral wall 42 is made of a polymer compound such as polyethylene, gelatin, or melamine resin.

  Therefore, when the temperature of the cooling water circulation path 30 (aluminum pipe 34) engine cooling water is equal to or higher than the phase transition temperature of the latent heat storage material 40, the heat absorbing portion 32 in which the heat storage body 38 is dispersedly held in the coating 36 is cooled. The latent heat storage material 40 undergoes a phase transition from a solid phase to a liquid phase by supplying heat from water, and as a result, the latent heat of fusion of the latent heat storage material 40 is deprived from the engine cooling water.

  Next, the operation of the first embodiment will be described.

  In the exhaust heat recovery system 10 configured as described above, heat exchange between the exhaust gas and the engine cooling water is performed in the exhaust heat recovery heat exchanger 18, and the heat of the exhaust gas is recovered in the engine cooling water (the exhaust gas is Cooled). Thus, for example, when there is a heating request or a warm-up promotion request for the engine 12 when the cooling water temperature is low, for example, immediately after the engine 12 is started, the heating of the exhaust gas is effectively used to promote heating or warm-up. Is fulfilled.

  Here, in the exhaust heat recovery system 10, since the heat absorption part 32 configured to include a large number of latent heat storage materials 40 (heat storage bodies 38) is provided in the cooling water circulation path 30, the engine cooling water temperature is the melting point of the peripheral wall 42. When the temperature reaches the above temperature, the heat absorption part 32 receives the heat from the exhaust gas, and the latent heat storage material 40 changes its phase from the solid phase to the liquid phase to take the latent heat from the engine coolant (heat absorption). . In particular, since the melting point of the latent heat storage material 40 is set to a temperature lower than the boiling point of the engine cooling water, the engine cooling water is prevented from boiling.

  For example, in a climbing condition (a condition in which traveling wind is weak with respect to the engine load) under a high load (condition in which the exhaust gas temperature is high) of an automobile to which the exhaust heat recovery system 10 is applied, heat exchange for the engine 12 and the exhaust heat recovery is performed. It is assumed that the amount of heat supplied to the engine coolant in the vessel 18 exceeds the cooling capacity of the radiator 28. In this case, for example, the temperature of the exhaust gas exceeds 600 ° C., and the tube wall constituting the exhaust heat recovery heat exchanger 18 in the exhaust pipe 14 is predicted to exceed 300 ° C. For this reason, in the configuration in which the latent heat storage material 40 (heat storage body 38) is provided in the exhaust heat recovery heat exchanger 18, the latent heat storage material 40 may be deteriorated (destroyed) by heat (high temperature) from the exhaust gas. is there. Further, in a configuration in which the latent heat storage material 40 (heat storage body 38) is a low-temperature side heat exchange medium or a configuration in which the heat storage body 38 is dispersed in engine cooling water, local heat generated in the heat exchanger 18 for exhaust heat recovery is generated. The latent heat storage material 40 may deteriorate due to stagnation, or the latent heat storage material 40 may deteriorate when the flow of engine cooling water stops.

  On the other hand, in the exhaust heat recovery system 10 in which the heat absorption part 32 is provided in the cooling water circulation path 30 that does not receive direct heat supply from the exhaust gas as described above, the radiator 28 capability without deteriorating the latent heat storage material 40. The excess heat of the engine coolant that is insufficient is temporarily absorbed by the latent heat storage material 40 to prevent the engine coolant from being abnormally heated (boiling). In particular, in the exhaust heat recovery system 10, the heat absorbing portion is provided in a portion including the heat exchanger outlet flow passage 30 </ b> A that flows immediately before the engine cooling water heated by heat exchange with the exhaust gas reaches the engine 12, which is another heat source. Since 32 is provided, boiling of the engine cooling water is reliably prevented. Further, the heat temporarily stored in a large number of latent heat storage materials 40 is discharged into the cooled engine cooling water or the atmosphere.

  Thus, in the exhaust heat recovery system 10 according to the first embodiment, overheating of the engine coolant can be prevented. Further, since the latent heat storage material 40 is used for the heat absorption part 32, the heat of the exhaust gas can be effectively used without taking heat from the engine coolant at a temperature equal to or lower than the phase transition temperature of the latent heat storage material 40. Furthermore, compared with the structure which provided the heat absorption part which takes sensible heat from engine cooling water, a heat absorption part can be comprised lightweight and compact.

  In addition, the latent heat storage material 40 can be easily microencapsulated, and the heat absorption part 32 can be configured with a simple structure by dispersing and holding the microcapsules in the coating 36.

  Next, a second embodiment of the present invention will be described. Note that parts and portions that are basically the same as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted, and illustration may be omitted.

  FIG. 4 shows a heat absorption part 52 constituting an exhaust heat recovery system 50 according to the second embodiment of the present invention in a cross-sectional view corresponding to FIG. As shown in this figure, the heat absorption part 52 is configured by dispersing and holding a large number of heat storage bodies 38 in rubber hoses 54 constituting the cooling water circulation path 30. Other configurations of the exhaust heat recovery system 50 are the same as the corresponding configurations of the exhaust heat recovery system 10.

  Therefore, also by the exhaust heat recovery system 50 according to the second embodiment, the same effect can be obtained by the same operation as the exhaust heat recovery system 10 according to the first embodiment.

  In the exhaust heat recovery system in which a part of the cooling water circulation path 30 is constituted by the aluminum pipe 34 and the other part is constituted by the rubber hose 54, the heat absorption part 32 and the heat absorption part 52 are both provided. It can be.

  Moreover, in each said embodiment, although the example using the latent heat storage material 40 microencapsulated by enclosing in the surrounding wall 42 was shown as a heat storage material which comprises the heat absorption part 32, this invention is not limited to this. For example, a heat storage material that removes heat from engine cooling water by an endothermic reaction (chemical reaction) such as a dehydration reaction at a predetermined temperature or higher (for example, a hydration reaction such as a mixture of zeolite and water or a salt containing crystal water) The endothermic portions 32 and 52 may be configured using a material that can reversibly generate a dehydration reaction.

  Furthermore, in each of the above-described embodiments, the example in which the circulating fluid of the internal combustion engine 12 is engine cooling water has been described. However, the present invention is not limited to this, and for example, the lubricating oil of the engine 12 is used as the circulating fluid. It may be applied.

It is a system flow figure showing typically the exhaust heat recovery system concerning a 1st embodiment of the present invention. It is sectional drawing which shows notionally the structure of the heat absorption part which comprises the exhaust heat recovery system which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows notionally the structure of the thermal storage body which comprises the exhaust heat recovery system which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows notionally the structure of the heat absorption part which comprises the exhaust heat recovery system which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

10 Exhaust heat recovery system (exhaust heat exchanger)
12 Internal combustion engine 18 Exhaust heat recovery heat exchanger (heat exchanger)
28 Radiator 30 Cooling water circuit (liquid circuit)
32 heat absorption part 40 latent heat storage material 50 exhaust heat recovery system (exhaust heat exchanger)
52 Endothermic part

Claims (4)

A heat exchanger for exchanging heat between the exhaust gas of the internal combustion engine and the circulating fluid circulating through the internal combustion engine;
A heat absorption part that is provided in a liquid circulation path for circulating the circulating fluid in the internal combustion engine and the heat exchanger, and absorbs heat from the circulating fluid when the temperature of the circulating fluid is equal to or higher than a predetermined temperature;
Exhaust system heat exchange device with   The exhaust heat exchanger according to claim 1, wherein the endothermic part includes a latent heat storage material that absorbs heat from the circulating fluid by phase transition, and a phase transition temperature is set to be equal to or lower than a boiling point of the circulating fluid. .   The exhaust heat exchanger according to claim 1 or 2, wherein the heat absorption part is provided in a portion where the circulating fluid flows from the heat exchanger toward the internal combustion engine in the liquid circulation path. The circulating fluid is an engine coolant for cooling the internal combustion engine.
The exhaust system heat exchange device according to any one of claims 1 to 3, wherein the liquid circulation path circulates the internal combustion engine, the heat exchanger, and a radiator through the engine coolant. .

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