EP2936040A1

EP2936040A1 - Heat exchanger comprising bypass channels

Info

Publication number: EP2936040A1
Application number: EP13864302.8A
Authority: EP
Inventors: Zoltan Kardos; Thomas HÄLLQVIST
Original assignee: Scania CV AB
Current assignee: Scania CV AB
Priority date: 2012-12-20
Filing date: 2013-11-27
Publication date: 2015-10-28
Also published as: RU2015129103A; BR112015014675A2; SE1251466A1; WO2014098714A1; EP2936040A4; SE536960C2; KR20150092288A; CN104919268A

Abstract

The present invention pertains to a heat exchanger comprising a container (3) which comprises an inlet section (3a), an intermediate section (3b) which encloses a heat exchanger device (5), and an outlet section (3c) where the first medium is led away from the heat exchanger device (5). The heat exchanger device (5) has a peripheral surface which in at least two areas is located at a distance from an internal surface in the container (3), so that at least two bypass channels (6a-d) are formed for the first medium next to the heat exchanger device (5). The heat exchanger comprises at least flow elements (7a-d) adapted to regulate the flow of the first medium through the bypass channels (6a-d). Each one of said flow elements (7a-d) has a first end section which is jointedly connected to the heat exchanger device (5) and a second free end section which is located at a distance from the heat exchanger device (5).

Description

Heat exchanger comprising bypass channels BACKGROUND AND PRIOR ART

The present invention relates to a heat exchanger according to the preamble of patent claim 1. The amount of air which may be added to an overloaded combustion engine in a vehicle depends on the pressure of the air, but also on the temperature of the air. In order to add as large a quantity of air as possible to an overloaded combustion engine, the charge air is cooled in an intercooler before it is led to the combustion engine. In conventional intercoolers, all charge air which is led to the intercooler is cooled. Under certain operational conditions it is, however, desirable to eliminate or at least reduce the cooling of the charge air. After, for example, a cold start of a vehicle, it is desirable that components for after-treatment of exhausts, such as for example an SCR-catalyst, quickly achieve a temperature at which it is possible to start the injection of a urea solution. In this case the cooling of the charge air delays the heating of the SCR-catalyst. In a vehicle it may also be desirable to regulate the cooling of other media such as, for example, recirculating exhausts in an EGR-cooler.

US 6,330,910 shows a heat exchanger which is intended to be arranged in an exhaust pipe in a vehicle. The heat exchanger comprises an external cylindrical body with an internally arranged coil for a refrigerant. In one embodiment shown, the external cylindrical body encloses an internal cylindrical body. The coil is in this case arranged inside the internal cylindrical body. The internal cylindrical body is arranged at a radial distance from the external cylindrical body, so that a peripheral channel is formed radially and externally to the internal cylindrical body. A throttle is arranged in an inlet opening of the internal cylindrical body, with which throttle the exhaust flow may be regulated via the internal cylindrical body. When the throttle is in an open position, the exhausts are led mainly through the internal cylindrical body where they are cooled by the medium in the coil. When the throttle is in a closed position, the exhausts are led outward to the peripheral channel which extends around the internal cylindrical body. When the throttle is in a closed position, the exhausts are subject to relatively large flow losses. SUMMARY OF THE INVENTION

The objective of the present invention is to provide a heat exchanger which has a com- pact construction, a good adjustability and low flow losses.

These objectives are achieved with the heat exchanger of the type specified at the beginning, which is characterised by the features specified in the characteristics of patent claim 1. The heat exchanger thus comprises a container with a preferably centrally ar- ranged heat exchanger device and a number of separate bypass channels which are arranged around the periphery of the heat exchanger. Since the bypass channels are arranged inside the container, they constitute an integral part of the heat exchanger. Such a heat exchanger may be given relatively small external dimensions and no separate, bulky bypass channel needs to be used to lead the medium around the heat exchanger device. In this case, the flow is regulated by each one of the bypass channels with the help of a respective flow element. Each one of the flow elements is jointedly connected to the heat exchanger at a first end section. The flow elements have a second free end section which may be adjusted to different positions as the flow element is turned in relation to the heat exchanger. With such flow elements, a simple and reliable regula- tion of the flow through the respective bypass channels is obtained. The heat exchanger has at least two bypass channels and thus at least two such flow elements. The heat exchanger advantageously has at least three bypass channels and thus at least three such flow elements. The end sections of the flow elements are preferably arranged so that the flow element forms a relatively small angle with the exhaust flow flowing into the heat exchanger, both when the exhaust flow is led through the heat exchanger and through the bypass channels. The flow channels advantageously have an angle in relation to the incoming exhaust flow which at least does not exceed 60° and preferably not 45°. Thus flow losses in the heat exchanger may be kept at a very low level. According to one embodiment of the present invention, the flow elements are arranged so that they may be turned between a first end position in which they block their respective bypass channels, so that the entire first medium flow is led through the heat exchanger, and a second end position in which they jointly block the flow through the heat exchanger device, so that the entire first medium flow is led through the bypass channels. The flow elements are thus arranged in such a manner that they essentially individually regulate the flow through the individual bypass channels, while they at the same time may act in concert to block the flow of medium through the heat exchanger device. The flow elements are advantageously adapted to abut with their free end sections against an internal surface in the inlet section, or in the outlet section, when they are in the first end position. Thus, the medium may be led essentially straight ahead and into the centrally arranged heat exchanger device without essentially changing direction, and out from the heat exchanger device without essentially changing direction. The flow elements are advantageously adapted to abut with their free end sections against each other in the second end position. The flow elements advantageously have a triangular shape with a broad base section, jointedly connected to the heat exchanger device, and a free end section which has a pointed shape. Such flow elements may in the second position form an essentially conical body where the free end sections form the tip of the cone. Such a conical body may entirely block the heat exchanger device's inlet while it relatively softly deflects media flow radially outwards to the bypass channels.

According to one embodiment of the present invention, said flow elements may be positioned in numerous intermediate positions between the first position and the second position, in which they lead a part of the first medium flow through the heat exchanger device and a remaining part of the medium flow through the bypass channels, with a distribution which varies between the intermediate position's distance to the respective end positions. The flow elements may be positioned in a determined number of fixed intermediate positions. However, they are advantageously continuously adjustable in random intermediate positions between the first position and the second position. In this case good possibilities of distributing the medium flow with optimal preci- sion through the heat exchanger device and the bypass channels are achieved.

According to one embodiment of the present invention the flow elements are at least partly arranged in the inlet section and/or in the outlet section of the container. In order to obtain an optimally structured medium flow it is suitable to arrange a first set of flow elements in the inlet section and a second set of flow elements in the outlet section. In this case, a steering of the medium flow is obtained both at the inlet and the outlet of the heat exchanger device. It is possible to arrange flow elements only in the inlet section or only in the outlet section, in order to obtain a desired distribution of the flow between the heat exchanger device and the bypass channels. However, in this case increased flow losses are obtained at that end of the heat exchanger device which lacks a flow element. According to one embodiment of the present invention, the container has an internal surface with eight sides and eight corners in a cross sectional plane, and a heat exchanger device having an external surface with four sides and four corners in said cross sectional plane, so that the heat exchanger device's four corners are fixed in every second corner of the container. With this design of the container and the heat exchanger device, a bypass channel is created radially externally of each of the heat exchanger's four sides. The attachment of the heat exchanger device's corners in the container's corners results in a rotation-fast attachment of the heat exchanger device inside the container. The heat exchanger device and the container may of course have other geometrical cross sections which result in the formation of separate bypass channels radially externally of the heat exchanger's sides. The heat exchanger device may for example have a triangular cross section, and the container a hexagonal cross section.

According to one embodiment of the present invention, the heat exchanger comprises a positioning mechanism, adapted to regulate the positions of all the flow elements in a synchronised manner, so that they are simultaneously placed in corresponding positions. In order for a structured and symmetrical medium flow to be obtained through the heat exchanger device, it is suitable for all flow elements to be regulated simultaneously and in a similar manner. In addition the number of driving elements comprised may be reduced with such a solution. Each one of the flow elements advantageously comprises a shaft which is attached in a rotation-fast manner in the heat exchanger device, while the adjacent flow elements' shafts are rotationally connected with each other. The shaft may consist of an elongated continuous shaft or consist of two coaxi- ally arranged and separate shafts. The shafts of adjacent flow elements may be rotationally connected to each other with the help of conical cogwheels. The adjacent flow elements' shafts form an angle in relation to each other. With the help of conical cogwheels, turning movements may be transmitted between two shafts which are at an angle in relation to each other. The turning movement between two such shafts may also be transmitted with the help of other types of components such as, for example, bendable pipe shaped elements which are fixed to the ends of the respective shaft and connected with each other. BRIEF DESCRIPTION OF DRAWINGS

Below is a description, as an example, of preferred embodiments of the invention with reference to the enclosed drawings, in which:

Fig. 1 shows a heat exchanger according to the present invention,

Fig. 2 shows a cross section through the heat exchanger in the plane A-A in Fig. 1 ,

Fig. 3 shows a longitudinal section of the heat exchanger in the plane B-B in Fig. 2 at an operational time when all air is led through the heat exchanger device, Fig. 4 shows a cross section of the heat exchanger in the plane C-C in Fig. 3, Fig. 5 shows a longitudinal cross section of the heat exchanger in the plane B-B in Fig. 2 at an operational time when a part of the air is led through the heat exchanger device and a part of the air is led through the bypass channels.

Fig. 6 shows a cross section through the heat exchanger in the plane C-C in Fig. 5, Fig. 7 shows a longitudinal cross section of the heat exchanger in the plane B-B in Fig. 2 at an operational time when all air is led through the bypass channels. Fig. 8 shows a cross section through the heat exchanger in the plane C-C in Fig. 7 and Fig. 9 shows a positioning mechanism according to one alternative embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Fig. 1 shows a heat exchanger. The heat exchanger is here exemplified as an inter- cooler 1 in a vehicle operated by an overloaded combustion engine. A first medium in the form of charge air is cooled in the intercooler 1. The intercooler 1 is arranged inside an air pipe 2 which leads charge air to the combustion engine. The intercooler 1 comprises a container 3, forming an external surface for the intercooler 1. The container 3 consists of an inlet section 3a, an intermediate section 3b and an outlet section 3c. The inlet section 3a has a successively increasing cross sectional area in a longitu- dinal direction, from a connection with a part of the air pipe 2 arranged upstream to the intermediate section 3b. The intermediate section has a constant cross sectional area. The outlet section 3c has a successively diminishing cross sectional area in a longitudinal direction, from the intermediate section 3b to a connection with a part of the air pipe 2 located downstream. A second medium in the form of a coolant circulates through the intermediate section 3b. The coolant is led into the intermediate section 3b via an inlet 4a, and out via an outlet 4b. Fig. 2 shows a cross section through the intermediate section 3b of the container in the plane A- A in Fig.1. This shows that the intermediate section 3b comprises a wall with an essentially constant thickness. The intermediate section 3b has a cross section in the form of an octahedron. The intermediate section 3b thus has a cross section with eight straight sides and eight corners. The inlet section 3a and the outlet section 3c also comprise a wall with a corresponding octagonal cross sectional shape. The intermediate section 3b encloses a heat exchanger device 5. The heat exchanger device 5 has a square cross sectional shape, defined by an upper side 5, a lower side 5b, a left side 5c and a right side 5d. The heat exchanger device 5 has four straight sides 5a-d and four corners. The four corners of the heat exchanger device 5 are attached to every second corner of the intermediate section 3b. Thus four separate areas are obtained, where there is a distance between the heat exchanger device's sides 5a-d and the sides of the intermediate section 3b. Thus four bypass channels 6a-d are formed radially externally of the heat exchanger's sides 5a-d. The heat exchanger device 5 in this case consists of longitudinal channels leading charge air between the end surfaces of the heat exchanger device 5 and coolant channels leading coolant in the opposite direction between the heat exchanger's end surfaces. Said channels are alternately arranged in the heat exchanger device 5, so that a large heat transition surface is formed between the charge air and the coolant in the heat exchanger device 5. The heat exchanger device 5 is in this case an upstream heat exchanger device, but it may of course also be designed as a downstream heat exchanger.

Fig. 3 shows a longitudinal section through the charge air cooler 1 in the plane B-B in Fig. 2. This shows that the heat exchanger device 5 in connection with the inlet section 3a and the outlet section 3c is equipped with flat shaped flow elements 7a-d. The flow elements 7a-d serve to control the flow of charge air through the intercooler 1. Each one of the flow elements 7a-d is equipped with a shaft 8a-d, attached in a rotation-fast manner in the heat exchanger 5. A first set of flow elements 7a-d are arranged in the inlet section 3a and attached to an inlet in the heat exchanger 5. A second set of flow elements 7a-d are arranged in the inlet section 3c and attached to an outlet in the heat exchanger 5. The flow elements 7a-d have an identical design and are thus equipped with the same reference numerals on both sides of the heat exchanger device 5. The flow elements 7a-d comprise, on each side of the heat exchanger device 5, four flow elements comprising an upper flow element 7a with a shaft 8a which is attached to the upper side 5 a of the heat exchanger device 5, and a lower flow element 7b with a shaft 8b which is attached to the lower side 5b of the heat exchanger device 5; a right side flow element 7c with a shaft 8c which is attached to the right side of the heat exchanger device 5, and a left side flow element 7d with a shaft 8d which is attached to the left side 5d of the heat exchanger device 5. The right and left flow elements 7c, 7d and the shafts 8c, 8d are not , however, visible in Fig. 3. The shafts 8a-d have end sections which are joined to connection elements, making the shafts 8a-d rotate in synchrony with each other.

A housing 9 is arranged over an opening in the inlet section 3a and a corresponding housing 9 is arranged over an opening in the outlet section 3c. Each one of the housings 9 encloses a positioning mechanism to position the flow elements 7a-d in the desired positions. The positioning mechanism comprises a control device 14 which controls the activation of a respective driving element 13 which is arranged in connection with the housings 9. Each one of the driving elements 13 is connected with a curved rack 11 via a cogwheel 10. Each one of the racks 11 is connected at one end to one of the flow elements, this case is the upper flow element 7a. Each one of the racks 11 extends from the upper flow element 7a, via said opening in the container 3, into the housing 9 where it is in contact with the cogwheel 10. By activating the driving elements 13, which may be electrical engines or pneumatic cylinders, the cogwheels 10 are made to rotate. When the cogwheels 10 rotate, they displace the racks 11 so that the upper flow elements 7a with shafts 8 are turned in relation to the heat exchanger device 5. Since the shafts 8a-d are rotationally connected with each other, all of the flow elements 7a-d undergo a simultaneous and corresponding rotation movement to the desired positions.

The flow elements 7a-d may be adjusted into a first end position, in which they block their respective bypass channels 6a-d. In this case, the entire flow of charge air is led through the heat exchanger device 5. The free ends of the flow elements 7a-d in this case abut against an internal surface in the inlet section 3a and in the outlet section 3c. Fig. 3 and 4 show the flow elements 7a-d in this first end position. The flow elements 7a-d may be adjusted into a second end position in which they, in a central position in the inlet section 3a and the outlet section 3c, respectively, abut against each other with their free end sections. The flow elements 7a-d here block the flow of charge air to the heat exchanger device 5. The flow elements 7a-d expose the bypass channels 6a-d, so that the entire charge air flow is led through the bypass channels 6a-d. Fig. 7 and 8 show the flow elements 7a-d in this second end position. The flow elements 7a-d may be continuously adjusted in a random intermediate position between said end positions. In this case a part of the charge air flow is led through the heat exchanger device 5 and a remaining part of the charge air flow is led through the bypass channels 6a-d. Fig. 5 and 6 show the flow elements 7a-d in such an intermediate position.

When the vehicle is driven, the control device 14 receives information indicating how large a part of the charge air flow that should be cooled. The control device 14 may receive information from, for example, a temperature sensor that detects the temperature in an exhaust purifying component, such as an SCR-catalyst in an exhaust pipe that leads exhaust away from the combustion engine. The temperature of the exhausts is related to the cooling of the charge air. As long as the temperature in an SCR- catalyst is below a certain temperature, the SCR-catalyst may not be activated. When this is the case, the control device positions the flow elements in the second position, so that that the entire charge air flow passes through the bypass channels 6a-d. Thus the charge air is not cooled, which results in a higher exhaust temperature and a faster heating of the SCR-catalyst, so that it may be activated and purify the exhausts relatively soon after a cold start. As soon as a desired operational temperature has been created in the exhaust pipe, the control device 14 positions the flow elements 7a-d normally into the first position. The entire exhaust flow is thus led through the heat exchanger device 5. The charge air thus provides optimum cooling. During certain operational times it may, however, be suitable to reduce the cooling of the charge air. In such cases the control device 14 positions the flow elements into a suitable intermediate position, so that only a specific part of the charge air flow is cooled in the heat exchanger device while a remaining part of the charge air flow is led through the bypass channels 6a-d without being cooled. With the help of the flow elements 7a-d, the cooling of the charge air may be regulated variably in the intercooler 1 with a good precision. The flow elements 7a-d form a relatively small angle to the charge air flow both in the first position, the second position and in the intermediate positions. Thus the charge air suffers very small flow losses in connection with the flow elements 7a-d. The intercooler 1 also has a very compact construction. It therefore requires a small mounting space in a vehicle.

Fig. 9 shows an alternative embodiment of a positioning mechanism. In this case the shafts 8a-d of the flow elements 7a-d are rotationally connected with each other with the help of conical wheels 12. It is apparent also here that the flow elements 7a-d have a triangular shape with a base section attached to a shaft 8a-d, and a free end section which constitutes a corner section in the flow elements 7a-d. An electric engine 13 is in this case connected with one of the shafts 8b. A control device 14 controls the activation of the electrical engine 13, and thus the position which the flow elements 7a-d take.

The invention is in no way limited to the embodiment described in the drawing, but may be varied freely within the framework of the patent claims. In the embodiment displayed, the flow elements 7a-d are arranged both in the inlet section 3a and in the outlet section 3c. One set of flow elements 7a-d, arranged in one of the said sections 3a, 3c to distribute the charge air among the heat exchanger device 5 and the bypass channels 6a-d, may suffice. The container 3 need not have an octagonal cross sectional shape and the heat exchanger device 5 need not have a square cross sectional shape. They may have other shapes resulting in the creation of bypass channels in peripheral areas between the heat exchanger device 5 and the container 3. The container 3 may, for example, be hexagonal and the heat exchanger may be trilateral. In this case, three bypass channels and three flow elements are created. According to the above, the heat exchanger 1 is not limited to being an intercooler but may, for example, constitute an EGR-cooler or any type of heat exchanger wherein it is desirable to adjust the heat transition between two media. The heat exchanger 1 is also not limited to being used in a vehicle. The media in the heat exchanger may be of essentially any type.

Claims

Patent claims

1. Heat exchanger comprising a container (3), which comprises an inlet section (3a) for receipt of a first medium, an intermediate section (3b) which encloses a heat exchanger device (5) where there is a heat transfer between the first medium and second medium, and an outlet section (3c) where the first medium is led out from the heat exchanger device (5), wherein the heat exchanger device (5) has an external peripheral surface area which in one area is located at a distance from an internal surface area of the container (3), a first bypass channel (6a) being formed for the first medium alongside the heat exchanger device (5), and wherein the heat exchanger comprises a first rotational flow element (5 a), adapted to regulate the flow of the first medium through the first bypass channel (6a), characterised by the heat exchanger device (5) having an external peripheral surface area which in at least one additional area is located at a distance from an internal surface area of the container (5), so that at least one additional bypass channel (6b-c) is formed for the first medium alongside the heat exchanger device (5), and wherein the heat exchanger comprises at least one additional rotational flow element (7b-d), adapted to regulate the flow of the first medium through the additional bypass channel (7b-d), wherein each one of said flow elements (7a-d) have a first end section jointedly connected with the heat exchanger device (5), and a second free end section located at a distance from the heat exchanger device (5).

2. Heat exchanger according to claim 1 , characterised by the flow elements (7a-d) being arranged in a rotation-fast manner between a first end position in which they block their respective bypass channels (6a-d), so that the entire first medium flow is led through the heat exchanger device (5), and in a second end position in which they together block the flow through the heat exchanger device (5), so that the entire first medium flow is led through the bypass channels (6a-d).

3. Heat exchanger according to any of the previous claims, characterised by the flow elements (7a-d) being adapted to abut against an internal surface in the inlet section

(3a) or in the outlet section (3c) with their free end sections, when they are in the first end position.

4. Heat exchanger according to any of the previous claims, characterised by the flow elements (7a-d) being adapted to abut against each other with their free end sections in the second end position .

5. Heat exchanger according to any of the previous claims 2 to 4, characterised by said flow elements (7a-d) being possible to position in a number of intermediate positions between the first position and the second position, in which they lead a part of the first medium flow through the heat exchanger device and a remaining part of the medium flow through the bypass channels (6a-d) with a distribution that varies with the intermediate position's distance to the respective end positions.

6. Heat exchanger according to any of the previous claims, characterised by the flow elements (7a-d) being at least partly arranged in the inlet section (3a) and/or in the outlet section (3c) of the container (3).

7. Heat exchanger according to any of the previous claims, characterised by the con- tainer (3) having an internal surface with eight sides and eight corners in a cross sectional plane and by the heat exchanger device (5) having an external surface with four sides and four corners in said cross sectional plane, so that the corners of the heat exchanger device (5) are attached to every second corner of the container (3).

8. Heat exchanger according to claim 1, characterised by comprising a positioning mechanism (10-14) which is adapted to regulate all the flow elements' (7a-d) positions in a synchronised manner, positioning them in the corresponding positions simultaneously.

9. Heat exchanger according to claim 8, characterised by each one of the flow elements (7a-d) comprising a shaft (8a-d), attached in a rotation-fast manner to the heat exchanger device (5), so that the shafts (8a-d) of the abutting flow elements are rotation- ally connected with each other.

10. Heat exchanger according to claim 9, characterised by the shafts (8a-d) of the abutting flow elements being rotationally connected with each other with the help of conical cogwheels (12).