Study on Thermal Conductivity Model for Porous PWR CRUD Depositions

Abstract In this study, corrosion product deposition test is carried out to measure effective thermal conductivity of CRUD depositions. Effective thermal conductivity is found to be a function of heat flux with an average value of 1.3866 W/(m × K). A thermal conductivity model for porous CRUD depositions based on statistically self-similar fractal scaling laws for pore size and capillary tortuousness is also developed to improve high-fidelity performance of CRUD internal heat and mass transfer prediction. The proposed model is expressed as an analytical expression of intrinsic thermal conductivities for solid skeleton and coolant phase, porosity and fractal dimensions for pore and tortuosity. Calculated effective thermal conductivity of CRUD depositions is also compared to the experimental data, showing an error maximum of 0.45 W/(m × K). It is also verified by experimental results in WALT Loop Rod 94 with cladding temperature error of less than 3.45 K and cladding superheat relative error of less than 9.25%. Additionally, the accuracy of the proposed model is compared with the existing models, showing better accuracy of cladding temperature prediction results. The study in this paper could capture microstructure characteristics and help understand heat transfer mechanisms of porous CRUD depositions, further promoting high-fidelity numerical simulation for CRUD depositions and related coupled multi-physical phenomena.