Effect of Heat Flux Distribution on Entropy Generation and Irreversibility of Lead-Bismuth Eutectic (LBE) Forced Convective Heat Transfer

Investigations on entropy generation and thermal irreversibility analysis are conducted for liquid lead-bismuth eutectic (LBE) in an annular pipe. To find better performance in convective heat transfer, the computational fluid dynamics (CFD) code based on the finite volume method (FVM) is adopted to solve this problem. The elevated temperature LBE flows in the annular pipe, and four types of heat flux, including constant, linear increase and decrease, and parabolic distributions are imposed at the inside wall of the annular pipe. The investigations are conducted for the specific average heat input of 200 kW/m², and the different Peclet number Pe is set from 1200 to 3200. The SST k-ω turbulent model and Cheng-Tak Pr_t model are adopted. The mesh independence validation and models verification are also conducted and the maximum Nu error is 5.43% compared with previous experimental correlations. The results from the local and system scales, respectively, including volumetric dimensionless entropy generation, Ns, Be, and E_p, are discussed. The results indicate that the viscous friction and heat transfer caused by entropy generation can be found in the viscous sub-layer and buffer layer respectively. Heat transfer is the primary factor that leads to irreversible losses. Besides, the results show that the best thermodynamic performance occurs under parabolic distributed heat flux in the research scope.