B.S. Pei

Evaluations and modifications of the EPRI-1 correlation on PWR critical heat flux predictions under normal and abnormal fuel conditions

The performance of five critical heat flux (CHF) correlations with the COBRA IIIC/MIT-1 code was evaluated. These correlations were evaluated against a data group comprised of 2943 axial nonuniform...

Experimental investigation of thermal mixing phenomena in a tee pipe

Abstract T-pipe designs have been widely used in the industry. Among them, mixing of hot and cold water is a common application. In the mixing process, cold and hot fluids are respectively injected through main and branch pipes, and are mixed in the downstream area of T-tube. High temperature hot water flows through the main pipe for a long time; hence, the pipe wall is at high temperatures. The fluid injected into the branch pipe is a cooling fluid. After mixing, the wall of the main pipe is under high thermal fluctuations causing strong thermal stresses, which will eventually lead to pipe damage and water loss. Through flow rate adjustments of the branch and main pipes, when the branch/main velocity ratio was greater than 7.8, showing that cold water hit the bottom of the main pipe and created a reverse flow. This reverse flow created large thermal stresses on the wall. Hence, the branch/main velocity ratio and the hot-water-mixing phenomenon are the focus of this study.

CFD Investigating the Effects of Different Mixing Vane Designs on the Localized Thermal-Hydraulic Characteristics in the Rod Bundles With Grid Spacer

A safe and reliable operation of a reactor system relies on the accurate thermal-hydraulic design in the rod bundles. With the dramatic progress in the computer processing power, computational fluid dynamics (CFD) methodology can be applied in investigating these thermal-hydraulic characteristics in details. The flow mixing devices on a grid spacer are generally designed to enhance the turbulence and heat transfer in the sub-channels. Therefore, the majority of this paper is to investigate the effects of different mixing vane configurations on flow pattern and heat transfer in the downstream of the mixing vanes in the rod bundles through CFD methodology. This CFD model is first assessed by the previous experiment of Holloway et al. In this study, six different designs of split-vane pairs are simulated, including (a) the split-vane 1 pairs (b) the split-vane 1 pairs without weld-nugget (c) the split-vane 2 pairs without weld-nugget (d) the Hybrid vane (e) the Swirl vane and (f) the SSVF vane. The thermal-hydraulic characteristics within the rod bundles with the split-vane pairs can be reasonably captured by the present CFD model, which includes the swirling secondary flow, turbulent mixing increase, and heat transfer enhancement, etc. Based on the comparison of Nusselt number distribution downstream the grid, the design of split-vane 1 pairs can enhance the heat transfer capability than other vane designs.Copyright