THERMO-HYDRAULIC INVESTIGATIONS OF A VERTICAL RECTANGULAR DUCT WITH LIQUID METAL FLOW BY MEANS OF SYSTEM CODE AND CFD CODE PREDICTION

摘要

In this paper, liquid metal flow in a vertical rectangular duct is investigated with respect to heat transfer and frictional losses. Thereby, the investigated channel is cooled with an Indium-Gallium-Tin alloy and the aspect ratio of the channel is 10:1. Liquid metal cooled systems gain more and more popularity in energy engineering (nuclear, fusion, solar power, heat storage, etc.) Therefore, comprehensive studies of relevant thermo-hydraulic phenomena are mandatory. In previous studies, it was demonstrated that liquid metal heat transfer cannot be approximated or represented by water or gas flows due to the non-similarity of the temperature and velocity fields. In addition, the majority of the liquid metal related investigations focused on circular channels and rod bundles. Rectangular channels are seldom investigated and experimental data are sparse. Some of the open questions of liquid metal thermo-hydraulics are detailed investigations of flow in rectangular geometries especially with asymmetric and in-stationary boundary conditions. Within this investigation, the heat transfer as a function of the Peclet number and the wall heat flux is analyzed. Furthermore, the pressure loss as a function of the Reynolds number is analyzed. The system codes TRACE and the CFD (Computational Fluid Dynamics) code OpenFOAM are used for the investigation. Thereby, one side is heated with a constant heat flux while the others are adiabatic or kept at constant temperature. Due to missing experimental data DNS (Direct Numerical Simulation) data will be used as a kind of reference solution in order to start a validation-like procedure based on code-to-code comparison. The investigations show, that rectangular channels with an aspect ratio of 10:1 can be considered as parallel plates. That means that a 2D representation for CFD codes is sufficient which reduces computational efforts compared to a 3D representation. The comparison between prediction and reference data shows the applicability of the assumptions made. Also, the comparison between system code and CFD code shows the agreement of the predictions. With this study, the confidence in the predicting capabilities of the two code options is fostered. Furthermore, these investigations will help to design experiments which are tailored to the needs of code and model validation.