Structural analysis of compact heat exchanger samples fabricated by additive manufacturing

Abstract

Compact heat exchangers are extensively employed in the industry due to their flexibility, geometric configuration characteristics, and the low ratio between heat transfer area by volume. Usually, these heat exchangers are exposed to high thermal and pressure gradients, which can cause structural failures during the operation. A new fabrication method employing additive manufacturing was evaluated to produce that equipment in this context. Twelve samples of 316L stainless steel that simulated a heat exchanger geometry were fabricated in two machines. A test rig was constructed for hydrostatic tests to evaluate their structural integrity through strain gauges. Some samples were submitted to pressures up to 700 bar without any leakage. The results show that printing orientation is crucial to the process, which influences material properties and, consequently, the von Mises stress observed. Properties on vertical orientation present lower stress levels. The influence of heat treatment was also verified, showing that machining processes locally alter mechanical properties. In parallel, a numerical study was developed for structural evaluation. It was observed that the pressurization of the distribution chamber strongly influences the stress of prototype channels. The high-stress region does not surpass the material yield strength for the test pressure. Furthermore, any deformation on the experimental prototype was not observed, indicating that the geometric characteristics guarantee a structural integer of the heat exchanger core. It is highlighted that the numerical results proved a good adherence to experimental results.