Patent Application
20170328637
The present invention relates to a heat exchanger comprising a pair of headers and a plurality of parallel and coplanar tubes interconnecting the headers, wherein each header comprises a header plate provided with a plurality of slots, in each of which an end of a respective tube is fitted, and wherein the heat exchanger is configured to prevent fluid from flowing into at least one tube, hereinafter dummy tube, arranged at a boundary between functionally different sections of the heat exchanger.
The invention relates in particular to the sector of heat exchangers for automobile engine cooling systems.
It is known to use radiators for the thermal treatment of the engine cooling fluid, in order to keep the engine at the optimum working temperature.
In particular, radiators which are divided into two or more functionally different sections in order to improve the cooling performance are known. For example, in this connection radiators characterized by a U flow of the cooling liquid are known, a first section of the radiator (which covers some of the tubes) being intended for the outward flow, and a second section (which covers the remainder of the tubes) being intended for the return flow of the cooling liquid. By way of a second example, so-called composite radiators are known, these being formed by single radiator bodies connected to separate high-temperature and low-temperature circuits, wherein a first section of the radiator (which covers some of the tubes) is connected to the high-temperature circuit, and a second section of the radiator (which covers the remainder of the tubes) is connected to the low-temperature circuit.
In the aforementioned cases, in the different sections of the radiator there exist different flows of the coolant at different temperatures, with the same or opposite flow directions. The sections of the exchanger are therefore at different temperatures; however, since they are in contact with each other within the same exchanger they may thermally influence each other.
In view of this drawback solutions have been proposed for improving the efficiency of a heat exchanger by preventing the thermal influence between adjacent or consecutive sections. In this connection, solutions have been proposed where the heat exchanger is configured to prevent the flow of fluid inside at least one tube, generally called a dummy tube, arranged at a boundary between functionally different sections of the heat exchanger.
For example, JP 2008-175508 A and JP 2002-115991 A are known solutions of composite heat exchangers in which the dummy tubes are created by placing partitions inside the headers which prevent the cooling fluid from being able to reach these tubes.
JP 2012-241600 discloses a solution where it is also envisaged placing, inside a composite radiator, a barrier block for preventing the dummy tubes from being effectively passed over by a cooling air flow.
In any case, in the known solutions, the creation of dummy tubes requires the positioning of partitions inside the headers. This represents a complication in the production process of the exchanger. Moreover, the solution which envisages the use of partitions cannot be used to create dummy tubes in a U-flow exchanger since the presence of a partition inside the recirculation header would create an interruption which would hinder the flow of the fluid.
In order to solve the problem of using partitions inside headers, it has been proposed to use dummy tubes which have a length smaller than that of the other tubes, so as not to perforate the header plates at the ends of these dummy tubes. This solution has however proved to be unsatisfactory owing to the difficulty of processing tubes of different lengths in automatic assembly machines.
One object of the invention is therefore to provide a solution for forming dummy tubes in a heat exchanger which is the simplest and most economical possible.
Another object of the invention is to provide a solution which may be used in exchangers with different flow configurations, in particular in U-flow exchangers.
These objects are achieved according to the invention by a heat exchanger of the type defined initially, in which the slot in the header plate which receives the end of the respective dummy tube is formed as a blind recess in the header plate, the end of the dummy tube being closed by an integral portion of the header plate.
Preferred embodiments of the invention are defined in the dependent claims which are to be understood as forming an integral part of the present description.
Further characteristic features and advantages of the invention will become clearer from the following detailed description of an embodiment of the invention, provided with reference to the accompanying drawings which are provided purely by way of a non-limiting example and in which:
With reference to
The heat exchanger 1 comprises a pair of headers 10, 20 and a plurality of parallel and co-planar tubes 30, 30′ which interconnect the headers 10, 20. Fins 40 are arranged between adjacent tubes 30, 30′.
With reference to
A plurality of slots 50, 50′ is formed in each header plate 11, 21, one end of a respective tube 3030′ being inserted in each of said slots. Each tube end is joined to either plate by means of a material connection, for example braze-welding, at each slot.
In the example shown, the heat exchanger 1 is an exchanger which has a U flow of the heat exchange fluid. One of the headers, denoted by 10 in
Inside the heat exchanger 1, therefore, two functionally different sections are identified: an outward section and a return section for the heat exchange fluid. The broken line B in
According to another embodiment of the invention (shown in
The heat exchanger 1 is configured to prevent the flow of fluid inside at least one tube, indicated by 30′ in the figures, arranged in the region of the boundary B between functionally different sections of the heat exchanger 1. The tubes in which the conveying of heat exchange fluid is prevented are known in the sector as dummy tubes and allow the thermal zones of the heat exchanger to be kept separate, preventing any mutual thermal influence and thus improving the performance features of the heat exchanger.
In the heat exchanger described above, the dummy tubes 30′ are entirely identical to the other tubes 30 which form the plurality of parallel and coplanar tubes of the heat exchanger. The flow of the heat exchange fluid to the dummy tubes 30′ is prevented by the fact that, in the header plates 11, 21, each slot, indicated by 50′, which receives the end of the respective dummy tube 30′ is formed as a blind recess in the header plate 11, 21, differently from the other slots, indicated by 50, which are formed as through-apertures. The end of the dummy tube 30′ is therefore closed by an integral portion of the header plate, in other words a portion, in particular a deformed portion, which forms part of the same plate part.
The configuration described above may be produced industrially in an extremely simple and low-cost manner.
In fact, in order to manufacture the header plates 11, 21, a plate conventionally undergoes a forming operation, in particular a deep-drawing operation, in order to form a plurality of deformed areas on the plate, each of which defines a blind recess.
The plate is then subjected to a material removal operation, in particular a punching operation, in order to form through-apertures in the deformed areas of the plate, the deformed areas provided with the through-apertures forming the slots 50 intended to receive the ends of respective tubes 30 of the heat exchanger.
In order to realize the configuration of dummy tubes described above it is merely required to omit the material removal operation in one or more of the deformed areas which form the slots 50′ intended to receive the ends of respective dummy tubes 30′.
To this end it is sufficient to modify or program the machine intended for the material removal (punching) operation such that it does not carry out the material removal operation in the deformed areas intended to form the blind-recess slots 50′. A same machine may therefore be adapted in an extremely simple manner to different header-plate configurations.
The dedicated moulds for forming the internal partitions in the header are therefore not needed, these being instead required in the known solutions and, among other things, being normally suitable only for a few types of header.
Moreover, as can be seen in the example shown, dummy tubes may also be provided in U-flow heat exchangers, something which would not be possible if separating partitions are arranged inside the recirculation header.
Moreover as can be seen, the present invention does not require the use of tubes of smaller length tubes for manufacture of the dummy tubes and therefore allows tubes all with the same length to be used. This aspect is particularly desirable with a view to automatic assembly of the heat exchanger.
