Header for a heat exchanger

A header of plastic material for a heat exchanger of the tube type has two identical faces provided with projecting ribs. The internal partition-wall of a water box is fitted between the ribs of one header face while the ribs of the other face are applied against an end fin of the tube bank.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a header for a tube-bank heat exchanger as well 
as to a heat exchanger which is equipped with said header and is primarily 
intended for use in the automobile industry. 
2. Description of the Prior Art 
In accordance with known practice, a header or tube sheet of a heat 
exchanger of this type can consist of a flat plate of rectangular shape 
provided with holes in which the tube ends are mounted in fluid-tight 
manner. These holes can be defined by tubular cylindrical collars which 
project from the plate in order to improve the leak-tightness of assembly 
of the tube ends. 
The header can be formed of plastic material in known manner, with the 
result that the fluid-tight tube ends can be mounted directly in the holes 
or collars of the header without interposition of seals. 
The water box which is mounted on the header in a conventional manner is 
usually formed of plastic material and secured to the header by 
seal-welding. In many designs, the water box has an internal 
partition-wall which extends at right angles to the header and the free 
edge of which has to be tightly applied against the header in order to 
divide the internal space of the water box into two chambers which are 
separated from each other in a substantially fluid-tight manner. 
When the heat exchanger is in service, a fluid circulates within said heat 
exchanger and in particular within the aforementioned water box, with the 
result that both faces of the internal partition-wall of said water box 
are continuously in contact with the fluid. In the course of time, this 
finally gives rise to deformations of said internal partition-wall, the 
free edge of which becomes detached from the header face on which it had 
been applied or fixed in a substantially fluid-tight manner. In 
consequence, the partition-wall between the two chambers of the water box 
no longer provides a fluid-tight separation. 
SUMMARY OF THE INVENTION 
The present invention is primarily intended to overcome this disadvantage 
and accordingly proposes a header for a tube-bank heat exchanger, said 
header being constituted by a plate of plastic material provided with 
holes for mounting the tube ends. The distinctive feature of the header 
lies in the fact that two parallel ribs are formed on the header face 
located externally with respect to the tube bank and that a groove is 
defined between said ribs and extends between said mounting holes. 
The above-mentioned groove is intended to receive the free edge of the 
internal partition-wall of the water box which is fixed on the header. 
Thus even if deformation of the internal partition-wall finally develops, 
the free edge of said partition-wall is permanently maintained within the 
groove located between the two parallel ribs of the header, thereby 
guaranteeing a substantially fluid-tight separation between the two 
chambers of the water box. 
According to another distinctive feature of the invention, the opposite 
face of the header is also provided with two ribs which are parallel and 
identical with the ribs of the other header face. 
The header can thus have a symmetrical structure since its two faces are 
identical with each other, thus removing any risk of error at the time of 
assembly of the heat exchanger. 
According to another distinctive feature of the invention, when the holes 
are defined by tubular collars which project from the header plate, said 
ribs have substantially the same height as said collars on each face of 
the header and extend along this latter in the longitudinal direction. The 
longitudinal orientation of the ribs can be defined as perpendicular to 
the flow of air through the tube bank when the heat exchanger is in 
service. 
When the heat exchanger is assembled, the ribs which are formed on the 
header face remote from the water box and which have the same height as 
the collars can come into contact with the end fin of the tube bank and 
can prevent any flow of air between the header and said end fin in a 
transverse direction, that is to say at right angles to the direction of 
said ribs. 
The invention further relates to a tube-bank heat exchanger comprising a 
header of the aforementioned type and a water box fixed on the header, 
said water box being formed with an internal partition-wall which is 
perpendicular to the header and one edge of which is received in the 
groove formed by the aforementioned ribs of the header. 
Said edge of the internal partition-wall of the water box is advantageously 
fixed in a fluid-tight manner, for example by seal-welding within the 
groove of the header.

DETAILED DESCRIPTION OF THE INVENTION 
The header 10 or tube sheet which is illustrated in FIGS. 1 and 2 consists 
of a flat plate of molded plastic having a rectangular contour in which 
are formed cylindrical holes 12 arranged in rows and in columns parallel 
to the edges of the plate 10 and defined by tubular cylindrical collars 14 
which project on each side of the plate and thus have a height exceeding 
the thickness of the plate. 
As illustrated in FIGS. 1 and 2, the ends of the collars 14 can be 
internally chamfered, with the result that the ends of the holes 12 are 
slightly flared-out. 
Each large face of the header comprises two projecting parallel ribs 16. A 
groove 18 is defined between said ribs and extends lengthwise along the 
header, for example along the longitudinal median axis 20 of this latter. 
The ribs 16 terminate in the vicinity of the ends of the header and 
therefore extend over the greater part of the length of this latter. 
Preferably, the height of the ribs 16 which form projections from the 
header plate 10 is substantially equal to the height of the collars 14. 
In the example of construction illustrated in the drawings, the ribs 16 
formed on one face of the header 10 are strictly identical with those 
formed on the other face and are symmetrical with these latter, with the 
result that the two header faces are strictly identical with each other. 
However, these ribs 16 could be relatively displaced from one header face 
to the other. 
Said header is intended to be employed in a heat exchanger which is partly 
illustrated in FIG. 3 and comprises a bank of parallel tubes 22 fitted 
with flat and parallel fins 24 through which the tubes 22 pass at right 
angles, the fins being secured to the tubes by crimping, for example. 
The ends of the tubes 22 are mounted in fluid-tight manner within the holes 
12 of the header by utilizing, for example, the elasticity of the plastic 
material forming the header. This known technique consists in inserting 
the ends of the tubes 22 in the holes of the headers, then in subjecting 
the tube ends to radial expansion by plastic deformation but without 
exceeding the elastic limit of the header material, then in reducing the 
radial tube-end expansion forces to zero. Under the action of their 
elasticity, the collars 14 which define the holes of the header are 
restored to their initial shape by producing radial shrinkage of the tube 
portions 26 located between two tube portions 28 and 30 which are not in 
contact with the header and which remain radially expanded. This has the 
simultaneous effect of achieving fluid-tightness between the tube ends and 
the header as well as locking the tubes within the holes of the header. 
When the tube ends are thus mounted in fluid-tight manner in the holes of 
the header, the end fin 24 of the tube bank is applied against the entire 
length of the ribs 16 formed on that face of the header 10 which is 
directed towards said fins. The end fin 24 is also applied at intervals 
against the ends of the collars 14 as shown in FIG. 3 when the ribs 16 and 
the collars 14 have the same height of projection from the header 10. 
A water box 32 of a conventional type (only part of which is illustrated in 
FIG. 3) is then mounted on the header 10 and secured to this latter by a 
method such as ultrasonic welding, for example. To this end, the water box 
32 has a peripheral flange 34 which is welded on the corresponding face of 
the header 10 in the vicinity of the periphery of this latter. 
The water box 32 is formed by molding with an internal partition-wall 36, 
the free edge 38 of which is received and welded within the groove 18 
which is delimited by the ribs 16 of the corresponding face of the header 
10. 
While the heat exchanger is in service, the edge 38 of the internal 
partition-wall 36 of the water box thus remains engaged between the ribs 
16 of the header and guarantees a fluid-tight separation between the two 
chambers which are delimited within the water box by said internal 
partition-wall 36. The deformations of said partition-wall 36, the two 
faces of which are continuously in contact with the fluid circulated 
within the heat exchanger, exert a stress at the level of the welded joint 
between the edge 38 of said partition-wall and the header but are not of 
sufficient magnitude to cause said edge 38 to escape completely from the 
groove which is limited by the ribs 16. 
As mentioned earlier, the ribs 16 formed on the other face of the header 
and applied against the end fin 24 of the tube bank form a barrier which 
prevents any circulation of air between the header 10 and the end fin 24 
of the tube bank in a direction at right angles to that of the ribs 16. 
When the two large faces of the header 10 are identical, said header can be 
mounted in one direction or in the other between the water box 32 and the 
tube bank, thus guarding against any risk of error at the time of assembly 
of the heat exchanger.