HEAT EXCHANGE FOR GAS, PARTICULARLY THE EXHAUST GASES OF AN ENGINE

Abstract

A heat exchanger (1) for gas, in particular the exhaust gases of an engine, comprising a bundle of tubes arranged inside a shell (2) and intended for the circulation of gas with an exchange of heat with at least one stream of refrigerant fluid, said tubes being fixed by their ends between two support plates (5) coupled at each end of the shell (2), and deflection means arranged inside the shell (2) able to direct the at least one stream of refrigerant fluid inside the shell (2). The deflection means comprises a longitudinal deflector (6, 6a) substantially parallel to the tube bundle and intended to divide the shell (2) into two circuits, said deflector (6, 6a) being fixed by its longitudinal edges to the internal walls of the shell (2) and by its transverse edges to the two support plates (5) by welding. This ensures more effective mounting of said deflector inside the exchanger.

Description

The present invention refers to a gas heat exchanger, in particular for the exhaust gases of an engine. The invention is particularly applicable to heat exchangers for exhaust gas recirculation in an engine (EGRC).

PRIOR ART OF THE INVENTION

In certain heat exchangers for cooling gases, for example those used in systems recirculating the exhaust gases to the intake of an internal combustion engine, the two media which exchange heat are separated by a partition.

The present configuration of EGR exchangers on the market corresponds to a metal heat exchanger generally made from stainless steel or aluminum.

There are essentially two types of EGR heat exchangers: the first type consists of a shell within which is arranged a bundle of parallel tubes for passage of the gas, the refrigerant circulating through the shell outside the tubes, and the second type consists of a series of parallel plates which constitute the heat exchange surfaces such that the exhaust gases and the refrigerant circulate between two plates in alternating layers, wherein the exchange of heat may be improved by the addition of fins.

In the case of tube bundle heat exchangers, the connection between the tubes and the shell may be of various types. Generally, the tubes are fixed by their ends between two support plates coupled to each end of the shell, the two support plates having a plurality of orifices for positioning the respective tubes.

Said support plates are in turn fixed to means for connection of the recirculation pipe, which may consist of a V connection or a peripheral connection edge or flange, depending on the design of the recirculation pipe where the exchanger is mounted. The peripheral edge may be mounted with a gas reservoir, such that the gas reservoir is an intermediate part between the shell and the edge, or the edge may be mounted directly on the shell.

In both types of EGR exchanger, the components are largely metallic such that they are mounted by mechanical means, then welded in the furnace or by arc or laser welding to ensure the adequate tightness required for this application. In certain cases, certain plastic components may also be included which may have a single function or various functions integrated into a single component.

The main function of EGR exchangers is the exchange of heat between the exhaust gases and the refrigerant fluid in order to cool the gases. Furthermore the EGR exchanger must fulfil other secondary functions so that it can be mounted on the engine block, allow connection with the refrigerant fluid, or allow connection with the exhaust gas circuit, amongst others. At present the various components of the exchanger are attached to the shell by furnace welding or by arc or laser welding.

Certain EGR exchangers with tubes or plates on the market have deflectors which are placed inside the refrigerant fluid circuit. The design and number of deflectors may vary from one application to the next, depending on usage requirements and restrictions from the vehicle manufacturer in terms of operating conditions or restrictions in presentation of the exchanger.

In most cases, deflectors are used to improve the circulation of refrigerant fluid around the gas tubes, thus avoiding stagnation points which could cause boiling of the refrigerant fluid inside the exchanger, and in order to improve refrigeration of all tubes for better efficiency of the exchanger.

In other cases, deflectors are included to prevent mechanical problems which could appear under the working conditions of the exchanger in the engine.

An EGR exchanger is known which uses a longitudinal deflector dividing the interior of the shell into two halves, in order to direct the refrigerant fluid in bypass mode from one half of the shell to the other when the inlet and outlet pipes for the refrigerant fluid are on the same side of the shell. This deflector is fixed to the shell of the exchanger by weld points and has a length slightly less than the length of the shell.

Spanish patent application number 200931016, not yet published, by the same holder as the present application, comprises a plurality of deflectors arranged transversely along the interior of the shell. Each deflector has a surface area smaller than the cross section surface area of the shell, which allows partial passage of the refrigerant fluid. Said deflectors are not aligned with each other but may be positioned alternately, leaving refrigerant fluid passage zones distributed alternately, thus ensuring correct distribution of the refrigerant fluid as well as improving the mechanical resistance to vibration.

In addition, said deflectors are fixed to the shell by furnace welding.

Patents JP2002292089 and JP2000283666 comprise a plurality of transverse deflectors in the form of plates arranged inside a shell of circular section. The design of said deflectors is very similar to the configuration of the support plates situated at both ends of the shell, the diameter of said deflectors being equal to the internal diameter of the shell, and comprise through openings which allow the passage of refrigerant fluid. The positions of said passage openings in the various deflectors are distributed alternately.

In general, the use of deflectors inside heat exchangers is common and has become more frequent in recent years, following environmental legislation and restrictions on the design of certain types of exchangers, such as:

• • heat exchangers which allow the use of two refrigerant fluid circuits, with the same or different fluids;
  • heat exchangers which must cool two hot fluids, being the same or different fluids;
  • heat exchangers in which the inlet and outlet pipes for the refrigerant fluid are on the same side of the shell.

The main problem posed by the use of deflectors is to ensure an adequate tightness between the two circuits defined in the shell of the exchanger when two types of refrigerant fluid are used, which is linked to the method of mounting and fixing the deflector inside the shell, generally by means of weld points, while ensuring the mechanical strength of the exchanger which must comply with the specifications of the vehicle manufacturer.

Another problem of this type of deflector is to be able to ensure the correct position and orientation of the deflector when it is mounted in the shell before being welded.

DESCRIPTION OF THE INVENTION

The aim of the gas heat exchanger, in particular for exhaust gases of an engine, in the present invention is to rectify the drawbacks of the exchangers known in the prior art by providing a deflector intended to improve the distribution of a refrigerant fluid circulating in the exchanger, or to separate two different refrigerant fluids without mutual communication inside the same shell, allowing a more effective mounting of said deflector inside the exchanger.

The heat exchanger for gas, in particular the exhaust gases of an engine, which is the subject of the present invention, is of a type which comprises a bundle of tubes arranged inside a shell and intended for the circulation of gas with an exchange of heat with at least one stream of refrigerant fluid, said tubes being fixed by their ends between two support plates coupled at each end of the shell, and deflection means arranged inside the shell able to direct the at least one stream of refrigerant fluid inside the shell, and it is characterized in that the deflection means comprises a longitudinal deflector substantially parallel to the tube bundle and intended to divide the shell into two circuits, said deflector being fixed by its longitudinal edges to the internal walls of the shell and by its transverse edges to the two support plates by welding.

This ensures easier positioning and mounting of the deflector inside the shell, and a better fixing thereof thanks to its weld connection. For preference, furnace welding is used, thus avoiding the use of weld points as in deflectors known in the prior art.

Advantageously, the deflector includes in its longitudinal edges two peripheral folded fins intended to come into contact with the internal walls of the shell for its connection by welding.

Also advantageously, the deflector includes in its transverse edges two protruding segments able to engage in respective grooves produced in the support plates for its connection by welding.

The use of said peripheral fins and protruding segments guarantees adequate positioning and orientation of the deflector inside the shell before it is fixed by welding.

According to a first embodiment, the deflector comprises a closed surface to prevent communication between the two circuits in the shell.

In this case the exchanger comprises two pairs of inlet pipes and outlet pipes provided for the distribution of two different streams of refrigerant fluid.

According to a second embodiment, the deflector comprises a through opening in its surface able to bring the two circuits into communication in the shell.

In this other case, the exchanger comprises a pair of inlet and outlet pipes arranged at the same end of the shell for the distribution of a stream of refrigerant fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

For better understanding of the description above, we attach drawings which depict diagrammatically, and merely as a non-limitative example, a practical embodiment of the heat exchanger for gas, in particular for the exhaust gases of an engine, according to the invention, in which:

FIG. 1 is a perspective and partial cross-section view of the heat exchanger of the invention, showing the location of the deflector and the two circuits through which two refrigerant fluids respectively circulate;

FIG. 2 is a perspective view of the deflector according to a first embodiment of the invention;

FIG. 3 is a perspective view of the deflector according to a second embodiment of the invention;

FIG. 4 is a perspective view of a type of exchanger which uses a same type of refrigerant fluid, with its inlet and outlet pipes situated at the same end of the shell;

FIG. 5 is a cross-section view of the exchanger in FIG. 4, showing the deflector used and the path of refrigerant fluid;

FIG. 6 is a perspective view of a deflector, showing the longitudinal fixing fins;

FIG. 7 is a partial, perspective view of the shell of the exchanger, showing the deflector mounted and fixed to the internal walls of the shell via the longitudinal fins;

FIGS. 8 and 9 are perspective and plan views respectively of an end of the deflector according to the invention, showing a protruding segment provided for engagement with a support plate of the tubes;

FIG. 10 is a perspective view of a support plate, showing an engagement groove intended to receive the protruding segment of the deflector;

FIG. 11 is a perspective view of the deflector mounted in the support plate illustrated in FIG. 10;

FIGS. 12 and 13 are respectively perspective views of two configurations of heat exchangers which use two different types of refrigerant fluid, showing the position of the respective pairs of inlet and outlet pipes of the two refrigerant fluids; and

FIG. 14 is a cross-section view in perspective of a heat exchanger using a single refrigerant fluid, showing the location of the pair of inlet and outlet pipes situated at the same end of the shell.

DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 shows partially a heat exchanger 1 which comprises a bundle of tubes (not shown for reasons of clarity) arranged inside a shell 2, defining an inlet and an outlet 4 for the gas, said tubes being intended for the circulation of gases with an exchange of heat with at least one refrigerant fluid. The tubes are fixed by their ends between two support plates 5 coupled at each end of the shell 2, the two support plates 5 having a plurality of orifices for positioning of the respective tubes.

Thus the exchanger 1 comprises deflection means arranged inside the shell 2 and able to direct the at least one refrigerant fluid in the shell 2. In this case, the deflection means comprises a longitudinal deflector 6 substantially parallel to the tube bundle and intended to divide the shell 2 into two circuits.

The deflector situated in the shell 2 of the exchanger 1 allows an improvement in distribution of a refrigerant fluid, or the separation of two different fluids, such as oil and a refrigerant fluid, without mutual communication inside the common shell 2. Two embodiments of the deflector are shown below.

According to a first embodiment shown in FIG. 2, the deflector 6 comprises a closed, homogenous surface which allows a perfect tightness between the circuits of the two refrigerant fluids. The purpose of said deflector 6 is to separate two different refrigerant fluids inside the shell 2 because of their different compositions, properties etc. This type of deflector 6 is used in exchangers in which it is necessary to use different refrigerant fluid circuits in the exchanger, in order to achieve the exchange of heat with the exhaust gases which circulate in the tubes.

FIG. 1 illustrates an exchanger 1 which uses said deflector 6 to separate two types of refrigerant fluid. In this case, two different inlet pipes 7, 7a and two different outlet pipes 8, 8a are necessary in the same exchanger 1. This ensures adequate separation of the refrigerant fluids in the same shell 2. FIG. 1 depicts the inlet and the outlet of the two refrigerant fluids in the shell 2, and the inlet and outlet of the gases in the shell 2 and their change of direction in a gas reservoir (not shown).

According to a second embodiment shown in FIG. 3, the deflector 6a comprises a through opening 9 in the surface for passage of a refrigerant fluid from one half to the other half of the shell 2, in order to optimize the distribution of the refrigerant fluid in the shell 6. This type of deflector 6a is therefore used to increase the efficiency or improve the distribution of the refrigerant fluid in the shell 2.

FIGS. 4 and 5 illustrate an exchanger 1 which uses said deflector 6a, the inlet pipe 7 and outlet pipe 8 of which are situated at the same end of the shell 2. On FIG. 4, the inlet and outlet of the refrigerant fluid in the shell 2 are indicated by arrows.

Because of restrictions in presentation or requirements from the vehicle manufacturer, it is possible that the inlet pipe 7 and outlet pipe 8 of the refrigerant fluid must be placed at a short distance from each other or even at the same end of the shell 2, which may create a preferential path for the refrigerant fluid and consequently affect the filling of the refrigerant fluid and lead to poor refrigeration of the gas tubes, and also give rise to stagnation points which may cause a phenomenon of boiling, risking damage to the exchanger. In this case, the deflector 6a with its opening 9 allows an improvement in the circulation of the refrigerant fluid in the exchanger.

The configuration of the deflector 6, 6a of the present invention includes folded peripheral fins 10 in its two longitudinal edges, as can be seen on FIG. 6, intended to connect the deflector 6, 6a to two internal partitions of the shell 2, preferably by furnace welding (see FIG. 7). In this way, the use of weld points between the deflector 6, 6a and the shell 2, as used with known deflectors of the prior art, is eliminated.

Thus the deflector 6, 6a of the present invention includes in its transverse edges two protruding segments 11, as illustrated by FIGS. 6, 8 and 9, able to engage in respective grooves 12 produced in the support plates 5 (see FIGS. 10 and 11), allowing the deflector 6, 6a to remain fixed in the appropriate position before it is welded. In this case, the deflector 6, 6a is mounted in a similar fashion to the mounting process of the tubes with said support plates 5.

For example, FIGS. 1, 12 and 13 illustrate respectively different configurations of exchangers 1 which use two refrigerant fluids, their respective inlet pipes 4, 4a and outlet pipes 8, 8a being arranged at different positions relative to the shell 2. In this case, a closed deflector 6 is used (see FIG. 2) to separate the two refrigerant fluids.

Secondly, FIGS. 4 and 14 show respectively different configurations of exchangers using a same refrigerant fluid, for which the pair of inlet 7 and outlet pipes 8 is situated at the same end of the shell 2, said pipes 7, 8 being arranged at different relative positions in the shell 2. In this case, a deflector 6a fitted with a through opening 9 (see FIG. 3) is used to improve the distribution of refrigerant fluid.

The deflector 6, 6a of the invention may be used in exchangers made of stainless steel or aluminum.

Claims

1. A heat exchanger for the exhaust gases of an engine, comprising:

a bundle of tubes arranged inside a shell for the circulation of gas with an exchange of heat with at least one stream of refrigerant fluid, said tubes being fixed by their ends between two support plates coupled at each end of the shell; and

deflection means arranged inside the shell able to direct the at least one stream of refrigerant fluid inside the shell, wherein the deflection means comprises a longitudinal deflector substantially parallel to the tube bundle and intended to divide the shell into two circuits, said deflector being fixed by its longitudinal edges to the internal walls of the shell and by its transverse edges to the two support plates by welding.

2. The exchanger as claimed in claim 1, wherein the deflector includes in its longitudinal edges two folded peripheral fins configured to contact the internal walls of the shell for the connection by welding.

3. The exchanger as claimed in claim 1, wherein the deflector includes in its transverse edges two protruding segments able to engage in respective grooves produced in the support plates for its connection by welding.

4. The exchanger as claimed in claim 1, wherein the deflector comprises a closed surface to prevent communication between the two circuits in the shell.

5. The exchanger as claimed in claim 4, which includes two pairs of inlet pipes and outlet pipes provided for distribution of two different streams of refrigerant fluid.

6. The exchanger as claimed in claim 1, wherein the deflector comprises a through opening in its surface able to bring the two circuits into communication in the shell.

7. The exchanger as claimed in claim 6, comprising a pair of inlet and outlet pipes arranged at a same end of the shell for distribution of a stream of refrigerant fluid.