JP2019039334A - Heat exchanger - Google Patents

Abstract

To improve cooling efficiency of a heat exchanger by suppressing boiling of a refrigerant in the heat exchanger.SOLUTION: The heat exchanger is provided that is installed in an intake passage or an exhaust passage of an internal combustion engine and transfers heat between gas and a refrigerant. The heat exchanger comprises a plurality of refrigerant passages, a gas passage, a water storage portion and a control portion. The plurality of refrigerant passages are disposed in parallel in a gravity direction and causes the refrigerant to flow in the gravity direction. The gas passage is a passage disposed between the adjacent refrigerant passages. The gas passage causes the gas to flow from one face side toward the other face side of opposed two faces in parallel with an arrangement direction of the plurality of refrigerant passages and the gravity direction. The water storage portion is formed at a lower portion of the gas passage, and stores condensate water generated in the gas passage. The control portion calculates an amount of condensate water stored in the water storage portion, increases a heat exchange amount in the heat exchanger when the calculated amount of condensate water is less than a threshold value, and decreases the heat exchange amount in the heat exchanger when the calculated amount of condensate water is the threshold value or more.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a heat exchanger. More specifically, the present invention relates to a heat exchanger that is installed in an intake passage or an exhaust passage of an internal combustion engine and exchanges heat between a refrigerant and intake or exhaust.

  Generally, a plurality of heat exchangers such as an intercooler and an EGR cooler are arranged in a vehicle. Specifically, for example, JP 2006-57473 A describes an EGR cooler. The EGR cooler has a refrigerant passage formed in a vertical or horizontal direction with respect to a horizontal gas flow direction.

JP 2006-57473 A

  The EGR cooler described in Japanese Patent Laid-Open No. 2006-57473 has a configuration in which a refrigerant circulates in a vertical and horizontal direction from a high temperature side to a low temperature side of a gas passage. In this case, the refrigerant may boil. Further, when the EGR cooler is used at low outside air temperature and low water temperature, condensed water may be generated in the EGR gas passage and remain inside. If the condensed water cannot be evaporated immediately after warming up, the parts may be damaged due to corrosion or freezing. Here, in order to avoid the generation of condensed water, it is preferable to limit the use of the EGR cooler to a condition in which condensed water is not generated, because this may lead to an increase in NOx emissions and a decrease in fuel efficiency. Absent.

  The present invention has been made to solve the above-described problem, and can suppress the boiling of the refrigerant in the heat exchanger and increase the cooling efficiency of the heat exchanger while suppressing the damage of the components due to the condensed water. An object of the present invention is to provide an improved heat exchanger.

  In order to achieve the above object, the present invention is a heat exchanger that is installed in an intake passage or an exhaust passage of an internal combustion engine and moves heat between a gas and a refrigerant, and includes a plurality of refrigerant passages and gas passages. And a water storage part and a control part. The plurality of refrigerant passages are arranged in parallel to the direction of gravity and allow the refrigerant to flow in the direction of gravity. The gas passage is a passage between adjacent refrigerant passages. The gas passage circulates gas from one surface side to the other surface side of two opposing surfaces parallel to the arrangement direction of the plurality of refrigerant passages and the gravity direction. The water storage part is formed in the lower part of the gas passage and stores condensed water generated in the gas passage.

  The control unit calculates the amount of condensed water accumulated in the water storage unit, and when the calculated amount of condensed water is less than the threshold value, increases the amount of heat exchange in the heat exchanger, and calculates the amount of condensed water When is equal to or greater than the threshold value, the heat exchange amount in the heat exchanger is reduced.

  The refrigerant passage is arranged so that the refrigerant flows in the direction of gravity, and gas is circulated between the refrigerant passages, so that the condensed water generated in the gas passage is lowered while suppressing the boiling of the refrigerant. Condensed water can be stored in the water storage part formed in the above, and deterioration of components due to the condensate water retention can be suppressed. Further, when the amount of condensed water is small, it can be stored even if condensed water is generated, so that the cooling efficiency of the heat exchanger is increased. On the other hand, when the amount of condensed water stored is large, the cooling efficiency of the heat exchanger is lowered. Thereby, since condensed water boils, the condensed water stored can be reduced, cooling gas by latent heat of vaporization.

It is a figure which shows typically the whole structure of the system of embodiment. It is a figure which shows typically the structure of the intercooler of embodiment. It is a flowchart for demonstrating the control routine which the control apparatus of embodiment performs. It is a figure which shows typically the other structural example of the heat exchanger of embodiment. It is a figure which shows typically the other structural example of the heat exchanger of embodiment. It is a figure which shows typically the other structural example of the heat exchanger of embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is simplified or omitted.

  FIG. 1 is a diagram schematically showing an overall configuration of a system according to an embodiment of the present invention. The system of FIG. 1 has an engine 2. The engine 2 has a supercharger 4. The compressor 12 of the supercharger 4 is disposed in the intake passage 10. An intercooler 14 is installed downstream of the compressor 12 in the intake passage 10. The intercooler 14 is a heat exchanger that cools the intake air compressed by the compressor 12 by heat exchange with the refrigerant. In the present embodiment, water is used as the refrigerant of the intercooler 14, but the refrigerant may not be water.

  The engine 2 also has an EGR device that recirculates part of the exhaust gas to the intake passage 10. The EGR device has an EGR passage 20 that connects an exhaust system and an intake system of the engine 2. An EGR cooler 22 is installed in the EGR passage 20. The EGR cooler 22 is a heat exchanger that cools the exhaust gas by exchanging heat between the exhaust gas and the refrigerant. In the EGR cooler 22 of the present embodiment, water is used as the refrigerant, but the refrigerant of the EGR cooler may not be water.

  A bypass passage 24 that bypasses the EGR cooler 22 is connected in parallel with the EGR cooler 22. A valve 26 that opens and closes the bypass passage 24 is provided at a portion where the bypass passage 24 joins the EGR passage 20. An EGR valve 28 that adjusts the amount of EGR gas is installed downstream of the valve 26 of the EGR passage 20.

  Although not shown, this system includes a control device. The control device is an ECU (Electronic Control Unit). In the present embodiment, the control device also has a function as a control unit for the intercooler 14 and the EGR cooler 22 that are heat exchangers. Various sensors and actuators of the engine 2 are electrically connected to the control device. The control device controls the entire system of the engine 2 and is mainly composed of a computer including a CPU, a ROM, and a RAM. Various control routines including routines described later are stored in the ROM.

  FIG. 2 is a diagram schematically illustrating the configuration of the intercooler 14. FIG. 2A illustrates a perspective view of the intercooler 14, and FIG. 2B illustrates a cross section taken along line AA in FIG. In FIG. 2, the left-right direction on the paper surface is the horizontal direction when the intercooler 14 is mounted on the vehicle, and the up-down direction on the paper surface is the vertical direction. The intercooler 14 is configured so that intake air flows in a substantially horizontal direction.

  As shown in FIG. 2, a plurality of tubes 30 for circulating cooling water are arranged in the intercooler 14 in parallel to the vertical direction. The tube 30 communicates with an inlet of cooling water formed on the upper surface of the intercooler 14 and an outlet of cooling water formed on the lower surface of the intercooler 14, and the cooling water is directed downward in the tube 30 in the vertical direction (that is, It is configured to circulate in the direction of gravity).

  Between the adjacent tubes 30, for example, plate-like fins 32 having a cross section formed in a wave shape or an uneven shape are arranged. A portion where the fins 32 are disposed, that is, an outer portion of the tube 30 is an intake passage 34 through which intake air flows. The fins 32 efficiently exchange heat between the cooling water in the tube 30 and the intake air. Further, the fin 32 may be configured to create a turbulence with respect to the flow of intake air.

  An intake inlet is formed on one side of the two opposing surfaces parallel to the tube arrangement direction of the intercooler 14 (that is, the horizontal direction in FIG. 2B) and the direction of gravity. Is connected. An intake outlet is formed on the other side of the two surfaces, and an outlet pipe 38 is connected thereto. The intake air is configured to circulate in the horizontal direction in the intake passage 34 from the inlet side to the outlet side.

  A lower portion of the intake passage 34 functions as a water storage unit 40. The intercooler 14 is configured such that the lowermost part B of the intake inlet pipe 36 and the outlet pipe 38 is located above the bottom surface C of the intercooler 14. In the intake passage 34, a portion from the allowable water storage position D below the lowermost part B to the bottom surface C of the intercooler 14 becomes the water storage part 40. In the figure, the size, shape, and horizontal position of the inlet pipe 36 and the outlet pipe 38 are substantially the same, but the size, shape, and horizontal position of the inlet pipe 36 and the outlet pipe 38 are different from each other. Also good. That is, also in this case, the water storage portion may be formed in a portion below the lowermost portion of the inlet pipe 36 and the outlet pipe 38.

  The condensed water generated in the intake passage 34 of the intercooler 14 by the configuration of FIG. 2 flows down in the direction of gravity in the intake passage 34 and is temporarily stored in the water storage section 40. The tubes 30 and the fins 32 are partially disposed in the water storage section 40 and are configured to be immersed in the condensed water accumulated in the water storage section 40.

  The EGR cooler 22 has the same configuration as the intercooler 14 described above. That is, the EGR cooler 22 has tubes arranged in parallel to the vertical direction and plate-like fins arranged between adjacent tubes so that the cooling water flows in the vertical direction downward. . In the EGR cooler 22, an exhaust passage is provided between the tubes. The lower part of the exhaust passage serves as a water storage part, and is configured to store condensed water.

  The control device is configured to calculate the amount of water condensation in the heat exchangers such as the intercooler 14 and the EGR cooler 22 and to perform control to change the heat exchange amount in the heat exchanger accordingly. Hereinafter, the control executed by the control device will be described.

  FIG. 3 is a flowchart for illustrating a control routine executed by the control device in the first embodiment. In the routine of FIG. 3, first, in step S100, it is determined whether or not the amount of stored water exceeds a threshold value. Here, the threshold value is set to a value that approximates the water storage amount when water is stored up to the allowable water storage position D in FIG. That is, the threshold is appropriately determined according to the amount of water that can be stored in the intake or exhaust passage of the heat exchanger. The currently stored value is used as the water storage amount in step S100. The amount of stored water is calculated and stored by a process described later.

  If it is determined in step S100 that the amount of stored water does not exceed the threshold value, the generation of condensed water is allowed, so the process proceeds to step S102 and the condensation mode is set. Next, it progresses to step S104 and control which increases the heat exchange amount in a heat exchanger is performed. Thereby, it will be in the state which is easy to generate | occur | produce condensed water, and the amount of condensed water storage can be increased. The control for increasing the amount of heat exchange in the heat exchanger includes, for example, control for increasing the amount of gas (that is, intake or exhaust) passing through the heat exchanger, or increasing the amount of cooling water, etc. Control that increases the cooling efficiency can be mentioned.

Next, the process proceeds to step S106, and the instantaneous condensation amount is calculated. The instantaneous condensation amount can be estimated according to the following equation (1), for example, in consideration of the amount of water stored in the heat exchanger. In step S106, the value calculated according to the following equation (1) is used as the instantaneous condensation amount.
Instantaneous condensing amount = (total heat exchanger volume x constant-volume decrease due to water storage amount) x gas amount x (steam amount-saturated steam amount) (1)

  In equation (1), the volume reduction due to the amount of stored water is calculated based on the currently stored amount of stored water. The amount of gas is the amount of gas flowing into the heat exchanger per unit time. The amount of steam is the amount of steam contained in the intake or exhaust, and is calculated according to the output of the humidity sensor in the case of the intercooler 14, and in the case of the EGR cooler 22, according to the amount of fuel and air. Is calculated. Further, the humidity saturated water vapor amount can be calculated based on the current temperature, pressure and the like.

  Next, the process proceeds to step S108, and the amount of condensed water stored is calculated and stored. Specifically, it is calculated by adding the instantaneous condensation amount calculated in step S106 to the currently stored amount of condensed water stored. Thereafter, the current process is temporarily terminated.

  On the other hand, if it is determined in step S100 that the amount of stored water is greater than the threshold, further generation of condensed water is not allowed. In this case, the process proceeds to step S112, the evaporation mode is set, and the process proceeds to step S114. In step S114, control for reducing the heat exchange amount in the heat exchanger is executed. Examples of the control for reducing the heat exchange amount in the heat exchanger include control for reducing the amount of gas passing through the heat exchanger, or control for reducing the cooling efficiency of the heat exchanger by reducing the amount of cooling water.

Next, it progresses to step S116 and the instantaneous evaporation amount of condensed water is calculated. The instantaneous evaporation amount can be estimated, for example, according to the following equation (2) in consideration of the water storage amount. In the process of step S116, the value calculated according to the following equation (2) is used as the instantaneous evaporation amount.
Instantaneous evaporation = (total heat exchanger volume x constant-volume decrease due to water storage) x gas quantity x (saturated steam quantity-steam quantity) (2)

  Next, proceeding to step S108, the amount of condensed water stored is calculated. Specifically, a value obtained by subtracting the instantaneous evaporation amount calculated in step S116 from the accumulated amount of condensed water stored is stored as the water storage amount. Thereafter, the current process is temporarily terminated.

  As described above, the intercooler 14 and the EGR cooler 22 that are heat exchangers in the present embodiment have a water storage section that stores condensed water in the lower part in the vertical direction of the gas passage (that is, the intake or exhaust passage). Have. Here, since water generates heat when condensing, in order to obtain the effect of vaporization latent heat, it is necessary to dissipate the condensed water. According to the configuration of the embodiment, the water in the vicinity of the hot gas can be effectively dissipated and the cooling efficiency is increased because the tubes 30 and the fins 32 are in contact with the water in the water storage unit 40. In addition, if the tube 30 and the fins 32 are immersed in the water storage section 40, the effect is increased, and water can be radiated by the entire tube 30 and the fins 32, so that the cooling efficiency is increased. be able to.

  In addition, for example, at high outside air temperature, high water temperature, and high load, the temperature can be lowered near the water surface of the water storage unit 40 by latent heat of vaporization, but the wall temperature increases toward the top. In this respect, in the present embodiment, the cooling water is cooled from the upper side toward the lower side, so that the upper portion of the heat exchanger having a small cooling effect due to vaporization latent heat can be effectively cooled.

  Further, according to the present embodiment, the amount of condensed water stored is calculated, and the amount of stored water is compared with a threshold value, so that the condensed water can be stored in the water storage unit 40 or the condensed water needs to be evaporated. Is judged. And the control which raises or lowers the heat exchange amount in a heat exchanger is performed by a judgment result. Thereby, in a state where the amount of stored water is small, condensed water is generated while cooling the gas by heat exchange with the cooling water, and the stored amount of water can be maintained at an appropriate amount. In a state where the amount of stored water is large, the amount of stored water can be maintained at an appropriate amount while increasing the cooling efficiency of the heat exchanger by utilizing the latent heat of vaporization of the stored water.

  In the present embodiment, a configuration has been described in which the lower portion of the gas inlet pipe 36 and outlet pipe 38 of the heat exchanger is the water storage section 40. However, the water reservoir is not limited to this configuration. 4 to 6 show other configuration examples of the heat exchanger.

  In the example of FIG. 4, a water storage part 52 is separately formed below the heat exchanger 50 so that the gas passages in the heat exchanger communicate with each other. Although illustration is omitted, in this example, tubes and fins are extended in the water storage section 52. Thereby, it will be in the state where the tube and the fin were immersed in the condensed water which accumulates in the water storage part 52, and can improve the cooling effect by vaporization latent heat.

  In the example of FIG. 5, a water collector 62 is installed separately from the heat exchanger 60. One end of a pipe 64 is connected to the water collector 62, and the other end of the pipe 64 is connected to the bottom of the heat exchanger 60. Thereby, the condensed water generated in the heat exchanger 60 is collected in the water collector 62. Further, when it is necessary to supply water to the heat exchanger 60, condensed water is appropriately supplied from the water collector 62.

  Moreover, as shown in the example of FIG. 6, a coating agent made of a substance that reacts with water may be coated on the surface of the water storage unit 40 in which condensed water is stored. Since the condensed water is configured to accumulate downward, the cooling efficiency can be increased by partial coating of only the water storage unit 40.

  In the above embodiment, when referring to the number of each element, quantity, quantity, range, etc., the reference is made unless otherwise specified or the number is clearly specified in principle. The invention is not limited to the numbers. Further, the structure and the like described in this embodiment are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

2 Engine 4 Supercharger 10 Intake Passage 12 Compressor 14 Intercooler 20 EGR Passage 22 EGR Cooler 24 Bypass Passage 26 Valve 28 EGR Valve 30 Tube 32 Fin 34 Intake Passage 36 Inlet Piping 38 Outlet Piping 40 Reservoir 50 Heat Exchanger 52 Reservoir 60 heat exchanger 62 water collector 64 piping

Claims (1)

A heat exchanger that is installed in an intake passage or an exhaust passage of an internal combustion engine and moves heat between a gas and a refrigerant,
A plurality of refrigerant passages arranged in parallel to the direction of gravity and circulating the refrigerant in the direction of gravity;
A passage between adjacent refrigerant passages, in which gas flows from one surface side to the other surface side of two opposing surfaces parallel to the arrangement direction and the gravity direction of the plurality of refrigerant passages Gas passage
A water storage part that is formed in a lower part of the gas passage and stores condensed water generated in the gas passage;
When the amount of condensed water accumulated in the water storage unit is calculated and the calculated amount of condensed water is less than a threshold, the amount of heat exchange in the heat exchanger is increased, and the amount of condensed water is equal to or greater than the threshold. In this case, a control unit configured to reduce the amount of heat exchange in the heat exchanger;
A heat exchanger.

Images