# Mechanical Integrity Analysis of a Printed Circuit Heat exchanger with Channel Misalignment
## 1 Introduction
Therefore, the mechanical integrity of the channel shape effect needs to be studied. A preliminary study on the mechanical integrity of the proposed design is needed and is the main purpose of this paper. Some studies on the structural integrity of PCHEs have also been conducted. [PERSON] et al. studied the structural integrity of an intermediate printed circuit heat exchanger for a SFR attached to supercritical carbon dioxide. It was found that the mechanical stress concentration occurred at the PCHE channel tip [12]. [PERSON] et al. also conducted a study on the structural integrity evaluation of a lab-scale intermediate PCHE in a very-high-temperature reactor (VHTR). Under the test conditions, the maximum Tresca stress was far below the allowable stress limit [13]. [PERSON] et al. conducted a structural design study of a plate-fin heat exchanger for HTGRs. In this study, we present a high-temperature structural design procedure for a plate-fin heat exchanger, which includes strength evaluation for primary stress and evaluation of creep-fatigue life [14]. [PERSON] and [PERSON] conducted a study on heat transfer in heat exchangers in sodium fast-cooled reactor systems. The practical Nusselt numbers of a heat exchanger were derived in the MONJU fast breeder reactor which was a Japanese sodium-cooled fast reactor [15]. The present study examined the stress distribution in a newly designed printed circuit heat exchanger model. This model is different to the common designs, which mainly use a semicircle channel shape. This shape is a combination of rectangular and ellipsoidal shapes, as shown in Figure 1. This PCHE design is planned to be manufactured through chemical etching and diffusion bonding processes. First, the canals that become the channel will be manufactured by chemical etching. Then, all layers will be stacked through diffusion bonding. In this case, the successful incorporation of a heat exchanger in a high-temperature nuclear service requires the manufacturer to be able to reliably produce high-quality diffusion welds. Because inspecting each weld in the core stack is impractical, the quality depends on a good understanding of the essential welding variables and strict control during the welding process [16; 17]. In the diffusion bonding process, misalignment may occur due to improper process control related to the temperature or pressure. Even though this misalignment can be controlled by strict variable controls during the bonding process, it is also essential to observe the effects of misalignment at the microscale, so that the limit corresponding to the safety factor can be set. In this paper, the misalignment phenomena that may occur in PCHE channels are modeled and simulated. A two-dimensional simulation using COMSOL Multiphysics is conducted to observe the effect of channel misalignment on the mechanical integrity of PCHE. Different misalignment conditions are modeled to compare the stress intensities. In addition to the structural integrity study, several previous studies have examined this misalignment problem. Weld misalignment influences the structural integrity of a cylindrical pressure vessel; in the most dangerous analysis case, a crack depth of 7 mm and allowable centerline offset of 8 mm resulted in a pressure limit of 3.15 MPa, which is still 0.65 MPa greater than the hydro test pressure [18]. Finite element analysis was conducted on cylindrical pressure vessels with a misalignment in a circumferential joint by [PERSON] et al. [19]. The results showed good agreement with [20]. The structural integrity of a steam generator tube sheet with an incorrectly drilled hole was evaluated according to ASME Section III construction code. The presence of incorrectly drilled holes or locally thin ligaments was found to not affect the primary stress margin in the tube sheet or reduce its overall structural integrity [21]. The finite element method (FEM) was used to investigate local stress concentrations due to the misalignment of welded structures and determine the effect of geometric variables.