Accelerated Life Testing of Heat Exchangers

Many different mechanical failure modes exist in all the fields of engineering. These failures can occur in simple, complex, inexpensive or expensive components of structures. Failure due to fatigue is the most common cause of mechanical failure [2, 4] for heat exchangers. Even if the number of mechanical failures compared to successes is minimal, the cost in lives, injuries and warranty dollars can be large. Proper fatigue design can reduce these undesirable losses. The closer the simulated analysis and testing are to the real product and its usage, the greater confidence in the engineering results. Reliability testing of these durability effects is critical in the definition of the risk level when launching a product to the field. In today's business environment warranty terms are increasing to match customers' expectations and the competitive business environment. Fatigue accelerated life testing of a microchannel heat exchanger, when properly conducted, needs to include numerical stress analysis to better select the stress levels the units under test (UUT) will be subjected to. Understanding of material properties and operational duty cycles allows the practitioner to accurately design a test representative of the actual product field performance. Designing a test that closely replicates the field behavior allows for a better estimation of the product reliability for a failure mode under field conditions. This paper presents a practical testing methodology used to determine a product's operational life from the application of operational temperature cycling, and the results are compared with field observations as part of a design improvement to a heat exchanger using an aluminum microchannel.