Patent Application
20080078533
Referring now to
The charge air cooler assembly 10 includes a core assembly 12 and two end caps 14. The core assembly 12 includes a plurality of tubes 16 and fins 18. Each tube 16 preferably extends across the width “w” of the core assembly 12. Additionally, each fin 18 preferably extends along the width of the core assembly 12. Preferably bounding the periphery of the core assembly 12 are side members 20 running across the width “w” and thickness “t” directions of the core assembly, and header members 22 running in the longitudinal “l” direction of the core assembly. The two end caps 14 are preferably welded onto the header members 22.
As seen in
Referring now to
Referring now to
The tube 16 has two layers, the tube housing 28 and an internal deposited layer 30. The tube housing layer 28 of the tube 16 is preferably formed of a conventional aluminum based material, and the internal deposited layer 30 is preferably formed of a corrosion resistant, thermally conductive, nonelectrolytic metallic alloy. The tube housing layer 28 has an outer surface 32, which defines the outer surface of the tube. An inner surface 34 of the tube housing layer 28 forms the surface upon which the internal layer 30 of corrosion resistant, thermally conductive, nonelectrolytic metallic alloy is deposited.
The turbulators 26 disposed within the tube 16 are preferably conventional aluminum turbulators. The turbulators 26 have the exposed surface 50, which is exposed to the fluid flow through the tube 16. The exposed surface 50 of the turbulators 26 also receive a layer 52 of the corrosion resistant, thermally conductive, nonelectrolytic metallic alloy.
The deposition of nonelectrolytic metallic alloys on metals has beneficial properties such as uniformity, excellent corrosion resistance, and excellent wear and abrasion resistance, although the invention should not be limited to these properties. A nonelectrolytic coating is produced by the controlled chemical reduction of metallic ions onto a catalytic surface. The reaction uses a reducing agent to supply electrons for the reduction (to cause the metal salts to be reduced onto an oxide-free catalytic surface). The reaction continues as long as the surface remains in contact with the bath solution or the solution becomes depleted of metallic ions.
Preferably, the corrosion resistant, thermally conductive, nonelectrolytic metallic alloy layer 30, 52 is a nickel phosphorus (Ni—P) alloy. Other preferable alloys include nickel phosphorus molybdenum (Ni—P—Mo) alloy, nickel tin phosphorus (Ni—Sn—P) alloy, cobalt phosphorus (Co—P) alloy, cobalt phosphorus manganese (Co—P—Mn) alloy, nickel copper phosphorus (Ni—Cu—P) alloy.
Depositing the alloy onto the tube housing layer 28 and onto the exposed surface 50 of the turbulator 26 can occur individually or simultaneously before the turbulator is brazed to the tube, or alternatively, the deposition can occur after the turbulator is brazed to the tube. Once a tube assembly 48 is formed, a conventional process for assembling a charge air cooler 10 can be used.
The advantage of depositing the nonelectrolytic metallic alloy onto the tube housing 28, (forming the internal layer 30) and also depositing onto the exposed surfaces 50 of the turbulator 26 (forming the outside layer 52), is that the interior corrosion resistance is addressed by the deposited alloy, with very little increase in weight as compared to an entirely stainless steel construction of tube and turbulator. Also, since aluminum is used as the base material, the construction is less costly than using a stainless steel construction. Further, since the tube housing layer 28 is formed of aluminum, the fins 18 can also be formed of aluminum, which further reduces weight and cost. Another advantage is that aluminum has higher thermal conductivity, which is a beneficial material property in a charge air cooler 10.
Since the header members 22 and the end caps 14 are relatively thick members compared to the tubes 16 and turbulators 26, a certain amount of corrosion of the these components can be tolerated without affecting the integrity or performance of the charge air cooler 10. For this reason, conventional materials (aluminum alloys, wrought aluminum) and processes can be used to produce the charge air cooler with the present tube assembly.
However, to further enhance the corrosion resistance of the charge air cooler 10, the inner surfaces of the header members 22 and the end caps 14 can also be coated with corrosion resistant, thermally conductive, nonelectrolytic metallic alloy.
While particular embodiments of the present heat exchanger have been shown and described, it will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the invention in its broader aspects and as set forth in the following claims.
