ANALYSIS OF THERMAL CRACK FORMATION IN WATER-CHARGED AIR-COOLED HEAT EXCHANGERS FOR HEAVY-DUTY VEHICLES

Abstract

The non-uniform flow distribution at the inlet severely affects the thermal cycling loading of the water-charged air-cooled (WCAC) systems resulting in crack formation after periods and hence leakage in the internal coolant. WCAC cracks are serious since having crucial effects on performance and durability. The thermal crack can be identified by testing the WCAC for various fatigue boundary conditions. The present study developed a custom thermal fatigue test rig to precisely determine the crack formation's location and cycle time in WCACs. The test rig was designed to reflect the vehicle's situation by simultaneously controlling the air and waterside of the WCAC continuously. Accordingly, the thermal fatigue tests of the WCAC parts were performed through the developed custom thermal fatigue test rig. The formation crack was observed periodically by carrying out tests with different critical cycles on the test rig, and the thermal cycling profile was generated. It was seen that the crack formation in the WCAC can be predicted at the same cycle time and exact location with the developed custom test rig compared to the vehicle tests. Moreover, the total cost, time, and man-hours per test increased by 80 %,75 %, and 60, % respectively, compared to traditional vehicle tests. Subsequently, the modified WCAC design was proposed to prevent non-uniform flow distribution at the inlet of the WCAC. The thermal fatigue tests of the modified WCAC design were performed using the developed test rig for stressful operating conditions. The results showed that the modified WCAC design is more robust to thermal fatigue than the old design. There was no crack formation in the modified WCAC design under various stressful operating conditions.