The present disclosure relates generally to heat exchanger tubes, and to combo-coolers including such heat exchanger tubes.
Two goals for heat exchanger manufacturing often include forming a product that exhibits efficient transfer of heat, while maintaining a relatively simple manufacturing process. In the automotive industry, in particular, it has also become desirable to combine multiple functions into a single heat exchanger assembly. Combo-coolers are an example of such an assembly and include multiple coolers. In a combo-cooler, the tubes of each cooler are connected to the same pair of manifolds. Oil coolers have been added to automotive combo-coolers. Such oil coolers often have a tube and fin structure, in part because of cost efficiency and ease of assembly.
Features and advantages of embodiments of the present disclosure will become apparent by reference to the following detailed description and drawings, in which like reference numerals correspond to the same or similar, though perhaps not identical, components. For the sake of brevity, reference numerals having a previously described function may or may not be described in connection with subsequent drawings in which they appear.
Embodiments of the heat exchanger tubes disclosed herein advantageously include multiple flow passages, and a varying wall thickness. It is believed that the varying wall thickness decreases thermal stress and improves thermal performance.
The inclusion of a standard oil cooler into a combo-cooler may increase thermal stress. This may be due, at least in part, to the fact that the tubes of the oil cooler and the tubes of the other coolers (e.g., the condenser) do not expand by the same amount (e.g., length), but are connected to the same manifold. The coefficient of thermal expansion is the same; however, due to the different temperatures, the thermal expansion of the tubes is different. For example, when hot oil flows inside the oil cooler, oil cooler tubes tend to expand, while at the same time, the condenser tube may be cooler, and thus not expand as much. In this case, the manifold may exert compression on the oil cooler tube and tension on condenser tube.
The present inventors have analyzed failure modes of oil cooler tubes using thermal cycle tests. The tests indicate that the weakest tube is generally the oil cooler tube positioned closest to the condenser. The tests also indicated that the oil cooler tubes were susceptible to the formation of micro-cracks, especially at a center of the tube. The micro-cracks would form at the center, and extend, in general, to the sides of the tubes. As used herein, the term “center of the tube” generally refers to the middle area of the tube when viewing a cross-section of a substantially flat tube, see, for example
Without being bound to any theory, the present inventors believe that by varying the thickness of the tube walls, and by increasing the thickness near the center, the formation of micro-cracks is substantially delayed or eliminated, thereby extending the life and performance of the tube. It is also believed that the varying thickness enhances the durability of the tube for withstanding thermal stress, thereby enabling additional flow passages to be formed in the tubes.
Referring now to
One of the inlets 114 and one of the outlets 116 service a first heat exchanger HE1, and another of the inlets 114 and another of the outlets 116 service a second heat exchanger HE2. Baffles 118 in each of the end tanks 110, 110′ separate the respective heat exchangers HE1, HE2 from each other. It is to be understood that additional baffles 118′ may be positioned within one or both end tanks 110, 110′ to direct the flow of fluid within a particular heat exchanger HE1, HE2.
It is to be understood that one or more of the tubes 10, 10′, 10″, 10′″ in the combo-cooler 100 includes flow passages (shown in
While a combo-cooler 100 is shown in
Examples of processes that may be used to form the tube 10, flow passages 14, and webs 16 include, but are not limited to extrusion, roll-forming, or bending and brazing.
The tube body 12 shown in
The tube body 12 also includes a wall 18 having a thickness (e.g., T1, T2, etc.) which varies over a width WT of the tube body 12. In one embodiment, the width WT (also known as core depth) of the tube body 12 ranges from about 8 mm to about 70 mm. Generally, the width WT of the tube body 12 extends from one side S1 to an opposed side S2. It is to be understood that the wall 18 thickness may vary across the width WT as is desired, however, as previously described, it may be particularly advantageous to form the thickest portion (see, e.g., thickness T4) at or near a center C of the tube body 12.
The thickness may vary gradually across the entire width WT (as shown in
In the embodiment shown in
Since the thickness of the wall 18 varies along the entire width WT of the tube body 12, the thickness also varies along the width WFP of each individual flow passage 14. As shown in
It is to be understood that in other instances (not shown in the Figures), the thickness along the width WT is not symmetrical, rather it increases extending from each of the two opposed sides S1, S2 toward some other predetermined point (i.e., other than the center C). In such embodiments, the thickness is asymmetrical.
Referring now to
In the embodiment shown in
Still further, it is to be understood that the portions P1, P2, P3 do not have to be aligned with the respective flow passages 14, and may be configured as is desirable for a particular end use. For example, the thickness T4 at the center C may be substantially consistent along the width WFP of the flow passage 14 directly adjacent thereto, while the rest of the wall 18 thickness T3, T2, T1 may gradually vary along the remainder of the width WT of the tube body 12 (e.g., as shown in
Referring now to
In
To further illustrate the embodiment(s) of the present disclosure, an example is given herein. It is to be understood that this example is provided for illustrative purposes and is not to be construed as limiting the scope of the disclosed embodiment(s).
A combo-cooler with 22 mm×4 mm tubes, each including 13 flow passages was formed. This combo-cooler has a varying thickness between the sides, and the thickness averaged 0.45 mm. The combo-cooler was exposed to thermal cycles until failure. A comparative combo-cooler with 22 mm×4 mm tubes, each including 12 flow passages and a uniform wall thickness (0.45 mm along the tube width) was also tested. The results are shown in Table 1 below.
The results clearly indicate that the varying wall thickness substantially enhances the life and efficiency of the tubes. Additional flow passages generally decrease tube resistance to thermal cycles. As such, it was expected that the combo-cooler including more flow passages would have failed prior to the combo-cooler having less flow passages. The results indicate that varying the wall thickness increases the durability of the tubes, thereby allowing additional flow passages to be formed therein and improving the thermal cycle performance.
Embodiments of the heat exchanger tubes 10, 10′, 10″ disclosed herein advantageously include a varying wall 18 thickness. It is believed that the varying wall 18 thickness, delays, decreases or eliminates the formation of micro-cracks at thicker areas, and reduces the amount of material used at thinner areas. It is also believed that the varying thickness also advantageously enhances the durability of the tube 10, 10′, 10″ for withstanding thermal stress, and enhances the overall efficiency of the combo-cooler 100.
While several embodiments have been described in detail, it will be apparent to those skilled in the art that the disclosed embodiments may be modified. Therefore, the foregoing description is to be considered exemplary rather than limiting.