Modeling and Analysis Support for High Temperature Single Heat Pipe Experiment: Current Status and Plan

This report summarizes the modeling and simulation activities under DOE microreactor program to support ongoing single heat pipe experiments with 7-hole core block at the SPHERE facility. The primary objective of these activities is to obtain preliminary insights into the current single heat pipe-cooled experimental facility, and based on that, support and guide the experimental efforts and test plans with the aim of producing high-quality experimental data.

Considering the current major interests of the single heat pipe experiment, i.e., (i) the startup behavior of liquid-metal heat pipe and (ii) the thermal stress of structural materials under high temperature operating conditions, the modeling and simulation efforts are being made in two respects:
(1) Development of a simplified conduction-based heat pipe analysis method for analyzing the liquid metal (sodium) heat pipe startup from a frozen state;
(2) A coupled thermal-structural modeling and analysis for SPHERE experiment (with 7-hole core block) and code-to-code benchmark.
As of February 2021, the theoretical development of the conduction-based heat pipe startup analysis model and the preliminary model performance tests using commercial CFD software have been completed. Also, the FEM-based coupled thermal-stress analysis model for the ongoing single heat pipe experiment has been created using the two commercial software packages (ABAQUS and STAR-CCM+), and the code-to-code benchmark study has been performed. The analysis results have led us to identify the limitations of the current models and future tasks for model improvement and validation.

Efforts will continue to use and further develop the modeling and analysis capabilities that have been built so far, to support ongoing single heat pipe experimental activities at the SPHERE facility such as measurement planning, data analysis, and potential design improvement study. In addition, continuing
collaboration with the NEAMS program is considered important so that the experimental data from SPHERE can satisfy the validation needs of Sockeye, a system-level heat pipe modeling software being developed with the support of DOE.