Investigation of Fatigue Characteristics for Heat Exchanger Tube in Air Conditioner: Effect of Surface Defect and Environmental Factor

Abstract

The objective of this study is to quantitatively analyze the static and fatigue characteristics of the repeated welding, operating temperatures, and surface defects (notches) in tubes with Al3003-O aluminum, which is applied to the heat exchangers. In particular, fatigue characteristics on actual aluminum tubes are evaluated. It was confirmed the grain size increases and the hardness decreases due to changes in the internal structure as the number of repeated welding increases. The fatigue limit of the aluminum tube at the operating temperature was 49.02 MPa which was lower than the room temperature. Also, the fatigue limit of the notched aluminum tube is measured to be 29.37 MPa which is reduced compared to that of the specimens without a notch; the fatigue notch factor is 1.67. Based on the Peterson equation, the material constants were derived by combining the results (fatigue notch factor, etc.) obtained through analysis and experiments. Derived material constants allow the prediction of fatigue limits for various defect (notch) sizes that may occur during the manufacturing and assembly of the heat exchanger. © 2023, The Author(s), under exclusive licence to Korean Society for Precision Engineering.