GB2051337A

GB2051337A - A tubular heat exchanger and a method of manufacturing the same

Info

Publication number: GB2051337A
Application number: GB8007212A
Authority: GB
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 1979-03-10
Filing date: 1980-03-04
Publication date: 1981-01-14
Also published as: FR2451562A1; FR2451562B3; DE2909514A1; GB2051337B

Abstract

In a tubular heat exchanger comprising tubes 2 for liquid coolant flow and close-spaced lamellar baffles 1 having tube receiving apertures circumscribed by cylindrical collars 3 by which said baffles are mounted on said tubes for heat-exchanging interaction with a gaseous heat- conveying agent, the invention provides collars (3) which at their free ends remote from the baffles (1) mounted on the tubes (2) extend into tongues (4) directed generally radially of the tubes (2) and serving to increase the heat exchanger capacity of the baffles (1). <IMAGE>

Description

SPECIFICATION A tubular heat exchanger and a method of manufacturing the same This invention relates to a tubular heat exchanger, and to a method of manufacture of a tubular heat exchanger, comprising tubes through which a liquid heat-conveying agent flows, and closely spaced lamellar baffles, located on the tubes so as to extend substantially at right angles to the axes of the tubes, for heat-exchanging interaction with a gaseous heat-conveying agent which flows around the tubes.

It has already been proposed in such heat exchangers to provide the baffles with apertures circumscribed by annular or cylindrical collars which abut closely against the external periphery of the tubes, Heat exchangers of this kind are often made from light metals and are used, for example, as water coolers for water-cooled vehicle internal combustion engines, the heat from the tubes through which the engine cooling water flows being transferred to the air baffles by way of their collars and then to the cooling air.During manufacture, the baffles are pre-perforated to a smaller diameter than the external diameter of the tubes at the locations at which the tubes pass through the baffles, the difference remaining between the diameter of the holes and the external diameter of the tubes being used by displacement of the metal concerned to form the collars, which are directed at right angles to the plane of the baffles.

The object of the invention is to improve the cooling capacity of such tube heat exchangers without incurring an increased expenditure on material.

The present invention accordingly provides a tubular heat exchanger comprising tubes through which a liquid heat-conveying agent flows, and dlosely spaced lamellar baffles located on the tubes for heat-exchanging interaction with a gaseous heat-conveying agent which flows around the tubes, said baffles having annular collars which abut closely against the external peripheries of the tubes with said baffles extending substantially at right angles to the tube axes, wherein the ends of the collars remote from the baffles extend into individual tongues which are bent in a direction away from the axes of the tubes.

Thus, by virtue of the invention, the heat transfer surface around which the cooling air flows is enlarged. The material required for this purpose is taken from the material which hitherto accrued as scrap during the perforating of the baffles, so that there is no requirement for additional expenditure on material which would increase manufacturing costs.

The transfer of heat is enhanced to best advantage if the tongues are bent into a plane lying substantially centrally between each adjacent pair of baffles.

Preferably, the tongues are uniformly distributed around the peripheries of the collars and their width decreases radially outwardly from the axes of the tubes.

The invention also provides a method of manufacturing a tubular heat exchanger as described above, in which the baffles are preperforated to a diameter substantially smaller than the external diameter of the tubes at the location at which the tubes are to pass through said baffles, the baffles are formed by a stamping or drawing operation performed on them concentrically with each hole, with cups having side walls and perforate bases, the side walls of said cups constituting said collars, the cup bases are cut or pierced to form them with a plurality of circumferentially distributed, radially extending incisions extending from the original edges of the holes to the collars, and the tongues thus produced are then first displaced to be at right angles to the plane of the baffles and are finally bent in a plane extending substantially parallel to the plane of the baffles.

Viewed over all, the invention improves the cooling capacity of the heat exchanger by enlarging the cooling surface at the air side, the material required for this purpose being taken from the material which was hitherto scrapped.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a plan view of a part of an air baffle of a tubular heater exchanger embodying with the invention, and Figure 2 is a section, to an enlarged scale, taken on the line Il--Il of Figure 1.

Referring to the drawings, lamellar air baffles 1 are made from relatively thin aluminium sheet and are drawn at a predetermined distance apart onto aluminium tubes 2 which carry a liquid heatconveying agent, particularly cooling water. The air baffles 1 are connected to the water tubes 2 by aperturing the baffles to create annular or cylindrical collars 3 at right angles to the plane of the baffles at the locations at which the tubes pass through them, so that the collars abut closely against the external diameters of the tubes. This close abutment is obtained, in general, by expanding the external diameters of the tubes until they abut against the cylindrical collars 3 of the air baffles 1 after the latter have been placed onto the tubes.

The spacing between the individual air baffles is obtained by providing them with upstanding surface projections or spacers (not shown) formed as by local piercing or punching operations.

In accordance with the invention, the cylindrical collars 3 continue in the form of individual tongues 4 which are bent so as to extend radially of the tubes. As is shown in greater detail in Figure 1, these tongues are uniformly distributed around the peripheries of the collars and their width decreases radially outwardly from the tube axes. It is advantageous to bend the tongues in a plane lying substantially centrally between two successive air baffles, as is shown by way of example in Figure 2. In this case, they project into a region of the flow of air which, passing equidistantly between the air baffles, has the lowest temperature and thus ensures a favourable heat transfer to the tongues.

During manufacture of the tongues, the air baffles can be pre-perforated at the locations at which the tubes pass through them, to a diameter which is smaller than that which was customary and necessary for forming the cylindrical collars 3 alone. Thus, for example, when using tubes having an external diameter of 8 millimetres, the air baffles are pre-perforated to a diameter of approximately 3.5 millimetres, whereas a diameter of approximately 6.7 millimetres has previously been customary for forming the cylindrical collars. Cups having side walls and perforate bases are then formed concentrically of these holes in a second working step which may conveniently be a pressing or a drawing operation, the side walls of the cups forming the collars 3 which subsequently abut against the tubes 2.

Radial incisions uniformly distributed around the periphery are then formed in the bottoms or bases of the cups by means of a cutting stamp or piercing tool and extend from the edges of the holes to the collars, that is, to the side walls of the cups. The radial tongues defined by these incisions are then displaced to be perpendicular to the plane of the air baffles by means such as a stamp or a press. Finally, the thus displaced tongues are again bent by a further stamp in a direction away from the axes of the tubes or the axes of the collars, as far as possible into a plane which lies approximately centrally between two adjacent air baffles.

The air baffles thus manufactured are drawn onto the aluminium tubes of the tube heat exchanger, the distance between the individual air baffles being determined by the spacers already mentioned above. Intimate connection between the external surfaces of the tubes and the collars of the air baffles is finally effected by expanding the tubes until they abut against the collars.

Compared with similar constructions hitherto in use, a tubular heat exchanger manufactured in this manner has a substantially larger heat-transfer surface on the air side which considerably increases the cooling capacity of the heat exchanger. The surfaces of the tongues additionally contribute to this increased cooling capacity by creating turbulence in the air passing between the air baffles and such turbulence may be further promoted, if desired, by curving the tongue surfaces.

In the drawings, the tubes have a circular crosssection, as is usually the case. However, without limiting the invention, it can be used with tubes of other cross-sections, such as oval or elliptical.

Claims

1. A tubular heat exchanger comprising tubes through which a liquid heat-conveying agent flows, and closely spaced lamellar baffles located on the tubes for heat-exchanging interaction with a gaseous heat-conveying agent which flows around the tubes, said baffles having annular collars which abut closely against the external peripheries of the tubes with said baffles extending substantially at right angles to the tube axes, wherein the ends of the collars remote from the baffles extend into individual tongues which are bent in a direction away from the axes of the tubes into a plane lying at least approximately centrally between the two baffles situated adjacent said collar.

1. A tubular heat exchanger comprising tubes through which a liquid heat-conveying agent flows, and closely spaced lamellar baffles located on the tubes for heat-exchanging interaction with a gaseous heat-conveying agent which flows around the tubes, said baffles having annular collars which abut closely against the external peripheries of the tubes with said baffles extending substantially at right angles to the tube axes, wherein the ends of the collars remote from the baffles extend into individual tongues which are bent in a direction away from the axes of the tubes.

2. A heat exchanger as claimed in claim 1, in which the tongues of each collar are bent into a plane lying substantially centrally between the two baffles situated adjacent said collar.

3. A heat exchanger as claimed in claim 1 or claim 2, in which the tongues of each collar are uniformly distributed around the periphery of said collar.

4. A heat exchanger as claimed in any one of claims 1 to 3, in which the width of the tongues decreases radially outwardly from the axes of the tubes.

5. A method of manufacturing the tubular heat exchanger claimed in any one of claims 1 to 4, in which the baffles are pre-perforated to a diameter substantially smaller than the external diameter of the tubes at the locations at which the tubes are to pass through said baffles, the baffles are formed by a stamping or drawing operation performed on them concentrically with each hole, with cups having side walls and perforate bases, the side walls of said cups constituting said collars, the cup bases are cut or pierced to form them with a plurality of circumferentially distributed, radially extending incisions extending from the original edges of the holes to the collars, and the tongues thus produced are then first displaced to be at right angles to the plane of the baffles and are finally bent in a plane extending substantially parallel to the plane of the baffles.

6. A tubular heat exchanger constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

7. A method of manufacturing the heat exchanger claimed in claim 6, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

New claims or amendments to claims filed on 14 August, 1980.

Superseded claims 1 and

2.

New or amended claims:-- New Claim 1.

Original Claims 3-7 to be renumbered as Claims 2-6 and appendancies corrected.