Rapid analysis of packed pebble beds for thermal–hydraulic characteristics via reduced order models

Abstract

In recent years, the pebble bed module has garnered increased attention due to its inherent safety and versatile applications, particularly in the form of High-Temperature Gas-Cooled reactors and fusion tritium breeding blankets. Understanding the thermal–hydraulic characteristics within the pebble bed is crucial for the safety evaluation and design of such reactors. To study pore flow in the pebble bed, discrete element coupling methods and computational fluid dynamics (DEM-CFD) are commonly employed. However, simulating thousands of pebbles can be computationally intensive and time-consuming. To address this, reduced order models (ROMs) have been developed to reduce the computational complexity by employing simplified systems instead of the original complex system, thereby significantly saving computational time while maintaining accuracy. In this work, ROMs have been established for body-centered cubic packing, face-centered cubic packing, and randomly packed beds of pebbles. Using the ROM results, subsequent analysis focused on two important thermal–hydraulic characteristics: pressure and effective thermal conductivity. A comparison was made between the results obtained from the full-order model (FOM) using CFD and the reconstructed ROM results. The case studies demonstrate the potential of the proposed approach in rapidly and accurately investigating significant flow and heat transfer features, such as pressure and temperature.