Session: DA-01-03 Design & Analysis of Heat Exchangers & Components

Paper Number: 60735

Start Time: Wednesday, July 14, 2021, 08:00 PM

60735 - Structural Integrity Assessment of a Unit Cell in a Laboratory-Scale Printed Circuit Heat Exchanger for Molten Salt Reactors With Supercritical CO2 Power Cycle 

Recently, the applications of supercritical carbon dioxide gain much more attention in solar and nuclear industries because of its low viscosity and high thermal conductivity. Meanwhile, to improve the heat transfer efficiency, high-pressure and high-temperature operation conditions are preferred. Therefore, Printed Circuit Heat Exchanger (PCHE) is considered as a promising technology to be employed in Molten Salt Reactors (MSRs) as an intermediate heat exchanger between the primary molten salt loop and the supercritical CO2 cycle, due to its highly compact construction, high heat transfer effectiveness, and capability of withstanding high pressures. However, the very high pressure difference (~15 MPa for sCO2 and ~0.1 MPa for the molten salt) and high temperature (500 – 700 °C) operating conditions may lead to potential failures of the heat exchanger. In this study, structural integrity assessment of a laboratory-scale PCHE that is made of Alloy 800H is performed using coupled thermal-mechanical simulations. To accurately predict the thermal stresses of the PCHE under prototypic operating conditions, Computational Fluid Dynamics (CFD) simulations are first performed using ANSYS FLUENT to obtain the temperature field of the PCHE. The CFD simulation is validated by experimental data, including the friction factor for the flow channel and heat transfer coefficient obtained from a high-temperature FLUoride Salt Test FAcility (FLUSTFA) constructed at the University of Michigan. In the mechanical simulations, to capture the plastic deformation inside the PCHE, the elastic-plastic analysis method is adopted. In addition, the strain-stress curves presented in the Draft ASME BPVC for use of the Alloy 800H (UNS N08810) at high temperatures, are used to develop a multilinear plasticity material model. The laboratory-scale PCHE is formed by diffusion-bonding the metal plates with semi-circular channels chemically etched. As a result, the sharp edges in the semi-circular channels are rounded by the diffusion bonding process and form fillets with a small radius. The fillet is helpful to reduce the stress concentration, but it is challenging to accurately measure its radius, which is a key parameter for the thermal-mechanical analysis. Thus, a sensitivity study is carried out for the fillet radius using the mechanical simulation tool to investigate the effects of fillet radius on the stress field.

Presenting Author: Shuai Che University of Michigan

Authors:

Shuai Che University of Michigan
Sheng Zhang University of Michigan
Adam Burak University of Michigan
Xiaodong Sun University of Michigan