Folded tube for a heat exchanger and method of making same

Details Folded tube for a heat exchanger and method of making same Folded tube for a heat exchanger and method of making same

1999-08-02

2001-04-03

Leo, Leonard (Department: 3743)

Metal working

Method of mechanical manufacture

Heat exchanger or boiler making

C165S177000, C165S183000

Reexamination Certificate

active

06209202

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to heat exchangers for motor vehicles and, more specifically, to a folded tube and method for making same for a heat exchanger in a motor vehicle.
2. Description of the Related Art
It is known to provide a tube for a heat exchanger such as a condenser in an air conditioning system of a motor vehicle. The tube typically carries a first fluid medium in contact with its interior while a second fluid medium contacts its exterior. Typically, the first fluid medium is a liquid and the second fluid medium is air. Where a temperature difference exists between the first and second fluid mediums, heat will be transferred between the two via heat conductive walls of the tube.
It is also known to provide corrugated fins or ribs in the interior of the tube to increase the surface area of conductive material available for heat transfer to cause turbulence of the fluid carried in the interior of the tube and to increase the burst strength of the tube. One known method of making such a tube is to physically insert a corrugated fin into the generally flattened tube after the tube has been manufactured. This is an extremely difficult process since the corrugated fin to be inserted into the tube is extremely thin and subject to deformation during the insertion process.
Another known method of forming a tube for a heat exchanger is to extrude the tube in an extrusion process. In this construction, internal ribs are formed during the extrusion. However, these extruded tubes are relatively expensive to produce.
Yet another known method of forming a tube for a heat exchanger is to provide a flat, elongated sheet with lugs and the ends of the sheet are folded to form the tube. The ends of the tube are then brazed. An example of such a tube is disclosed in U.S. Pat. No. 5,386,629. In this construction, the tube may have flow paths between the lugs having a hydraulic diameter of less than 0.050 inches. Hydraulic diameter is conventionally defined as the cross-sectional area of each of the flow paths multiplied by four and divided by a wetted perimeter of the corresponding flow path. While a hydraulic diameter of less than 0.050 inches optimizes heat transfer efficiency, it is relatively expensive to produce.
Although the above tubes have worked well, they suffer from the disadvantage that the extruded tubes are relatively costly to manufacture Another disadvantage of the above tubes is that the lugs are not folded and squeezed. Yet another disadvantage of the above tubes is that the hydraulic diameter of the flow paths are not greater than 0.050 inches, making them relatively expensive to produce. Therefore, there is a need in the art to provide a folded tube for a heat exchanger of a motor vehicle that overcomes these disadvantages.
SUMMARY OF THE INVENTION
Accordingly, the present invention is a folded tube for a heat exchanger. A folded tube includes a base, a top spaced from and opposing the base, a first side interposed between the base and the top along one side thereof, and a second side interposed between the base and the top along another side thereof. The folded tube also includes at least one of the base and the top having at least one internal web having an initial web height and being compressed to extend the at least one internal web to a final web height greater than the initial web height and defining a plurality of fluid ports.
Also, the present invention is a method of making a folded tube for a heat exchanger. The method includes the steps of providing a generally planar sheet, folding the sheet, and forming at least one internal web having a first fold portion and a second fold portion. The method also includes the steps of compressing the at least one internal web to extend a height of the at least one internal web. The method further includes the steps of folding the sheet and forming a base and a top opposing the base and a first side interposed between the top and the base and a second side interposed between the top and the base such that the at least one internal web contacts either one of the top or the base to provide a plurality of fluid ports.
One advantage of the present invention is that a folded tube for a heat exchanger such as a condenser is provided for an air conditioning system of a motor vehicle for condensing liquid refrigerant. Another advantage of the present invention is that the folded tube is stamped and folded and is more economical to manufacture than an extruded tube. Yet another advantage of the present invention is that the folded tube can have multiple ports or flow paths with a hydraulic diameter greater than 0.070 inches, making it relatively inexpensive to manufacture. Still another advantage of the present invention is that the folded tube is able to meet performance requirements.
Other features and advantages of the present invention will be readily appreciated, as the same becomes better understood after reading the subsequent description taken in conjunction with the accompanying drawings.


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