Abstract The Printed Circuit Heat Exchanger (PCHE) is an important candidate to be used as Intermediate Heat Exchangers (IHX) in High Temperature Gas-cooled Reactor (HTGR) due to its advantages in terms of heat transfer and compactness. However, the complex operating conditions that include fluid temperatures around 1173 K and pressures higher than 7 MPa, cause the structural integrity of the device must be investigated in depth. In this work, a computational model of a PCHE with two-dimensional specification was developed using computational fluid dynamics and finite element method to evaluate the thermal and mechanical stresses. The simplification of the geometric domain was done considering the sensitivity of the stresses in the channels wall. The influence of the temperature gradient and the geometric parameters on the thermal stress is presented. The mechanical stress caused by pressure was evaluated for different geometric designs in the channel wall. The temperature gradient between channels was changed in a range from 10 K to 250 K, and the design was studied by means of parameters as channel diameter, plate thickness, ridge thickness and rounded tip radius. The isochronous strain–stress curves presented in the Draft ASME BPVC for use of the Alloy 617 (UNS N06617) at high temperature, were used to develop a multilinear plasticity material model. A proportional relationship between the thermal stress and the thermal gradient between channels was found. Opposite effects of the plate thickness and the ridge thickness on the thermal and mechanical stresses were evidenced. The increase of these produced a maximum thermal stress increment while the mechanical stress was reduced. The rounded tip radius was found as the main dimension to reduce both stresses reducing the stress concentration in this region. Based on the allowable stress of the structural material, safety ranges of the geometric parameters in the PCHE design were proposed. The plastic strain was also reduced with the roundness, but this displacement showed a great affectation with the time of service at high temperature condition.

中文翻译：

---

极高温条件下设计对印制电路换热器结构性能影响的评估

摘要 印刷电路换热器（PCHE）由于其传热和紧凑性方面的优势，是高温气冷堆（HTGR）中用作中间换热器（IHX）的重要候选材料。然而，复杂的操作条件包括大约 1173 K 的流体温度和高于 7 MPa 的压力，导致必须深入研究设备的结构完整性。在这项工作中，使用计算流体动力学和有限元方法开发了具有二维规格的 PCHE 计算模型，以评估热应力和机械应力。考虑到通道壁中应力的敏感性，对几何域进行了简化。介绍了温度梯度和几何参数对热应力的影响。对通道壁中不同几何设计的压力引起的机械应力进行了评估。通道之间的温度梯度在 10 K 到 250 K 的范围内变化，并通过通道直径、板厚、脊厚度和圆角尖端半径等参数研究设计。在 ASME BPVC 草案中提出的用于高温下使用合金 617 (UNS N06617) 的等时应变-应力曲线用于开发多线性塑性材料模型。发现了热应力和通道之间的热梯度之间的比例关系。证明了板厚度和脊厚度对热应力和机械应力的相反影响。这些的增加产生了最大的热应力增量，而机械应力降低。发现圆形尖端半径是主要尺寸，以减少两个应力，从而减少该区域的应力集中。根据结构材料的许用应力，提出了PCHE设计中几何参数的安全范围。塑性应变也随着圆度的增加而减小，但这种位移随着高温条件下的使用时间显示出很大的影响。提出了 PCHE 设计中几何参数的安全范围。塑性应变也随着圆度的增加而减小，但这种位移随着高温条件下的使用时间显示出很大的影响。提出了 PCHE 设计中几何参数的安全范围。塑性应变也随着圆度的增加而减小，但这种位移随着高温条件下的使用时间显示出很大的影响。