Long Life, Heavy Duty, Air-to-Air Charge Air Cooler 981974
This paper describes a new long life, heavy duty, air-to-air charge air cooler (CAC) which has particular application in heavy duty trucks, buses, off-highway vehicles and construction equipment. In this paper, it is proven through structural modeling and fatigue analysis on actual service histories that plastic flow and the resulting cumulative damage make it impossible for a typical brazed charge air cooler to meet minimum reliability requirements in at least some applications. Thermal expansion of the charge air cooler core, internal pressure, and external shock and vibration all contribute to a complex stress/strain response behavior in the area of the tube-to-header joint. Testing showed that the use of resilient tube-to-header joints, utilizing grommeted seals between the tubes and headers, eliminates the high stresses in this area and provides a theoretically infinite life. To adapt the concept of resilient tube-to-header joints to low cost assembly and manufacturing techniques, a radically new cast manifold was perfected, having an integral header with cast openings to receive the grommets and tubes. The resulting charge air cooler assemblies have zero leakage as manufactured and have maintained this condition indefinitely during field tests, confirming that the new design will provide the kind of long life required for heavy duty applications. Patents have been applied for.