Impacts of internal heating on temperature distribution in channels

TL;DR

This study investigates how internal volumetric heating affects temperature distribution in channels within molten-salt reactors, using multi-scale simulations to inform modeling approaches and reactor safety analysis.

Contribution

It introduces a combined DNS, LES, and semi-analytical approach to quantify internal heating effects across various flow regimes, providing new insights and guidelines for reactor modeling.

Findings

Internal heating effects are secondary at high Reynolds numbers in turbulent flows.

Lower Reynolds and higher Prandtl numbers increase the significance of volumetric heating.

The semi-analytical solver effectively explores broad parameter spaces with acceptable accuracy.

Abstract

In molten-salt-fuelled reactor systems, the fluid may experience substantial volumetric heat generation in addition to heat removal from surrounding structures. To quantify these effects, we investigate developed channel flow with internal heating using a systematic multi-scale approach comprising Direct Numerical Simulation (DNS), Large Eddy Simulation (LES), and a semi-analytical solver (SAS). First, DNS and LES are compared in a turbulent parallel-plate configuration at different Prandtl and Reynolds numbers, demonstrating excellent agreement in flow and thermal fields, with the SAS method showing acceptable accuracy. Building on this benchmarking, the SAS tool is then employed to explore a broad parameter space, offering insights into how internal heat deposition modifies the temperature distribution across Reynolds and Prandtl numbers. Comparisons are also drawn against the canonical wall-heating scenario, revealing that volumetric heating often remains a secondary effect in turbulent regimes but can become more pronounced at lower Reynolds numbers, higher Prandtl numbers, or when nearly all heat is deposited in the fluid. These findings establish guidelines for reduced-order modeling in liquid-fuel reactor analyses and highlight conditions under which internal heating warrants particular attention. The paper concludes by outlining ongoing and future research directions, including refinements for variable fluid properties and complex geometry extensions.