Heat Transfer Characteristics of Three-Dimensional Surface Roughness in Nuclear Fuel Rod Bundles

This paper presents convective heat transfer results for enhanced surface rod bundles for a pressurized water nuclear reactor (PWR). The experiments, to determine the single-phase heat transfer characteristics, were performed in a Single Heater Element Loop Tester (SHELT). The heater element simulates a single fuel rod for PWR. In this experimental investigation, the effects of enhancing the outer surface roughness of a simulated nuclear fuel rod bundle were studied. The outer surface of the simulated fuel rod was created with a three-dimensional (Diamond-shaped blocks) surface roughness. The simulated rod was made of Inconel 615, and was supported by Nickel 200 rods. Joule heating was supplied to the rod by passing electric current through the rod. The rod had an outside diameter of 9.5 mm and wall thickness of 1.5 mm, placed in a test-section made of 38.1 mm inner diameter aluminum pipe with a wall thickness of 6.35 mm. Tests were conducted for Reynolds numbers ranging from 10(5) to 10(6). Enhancement in heat transfer coefficient at all Re was recorded. The maximum heat transfer co-efficient enhancement recorded was 86% at Re = 4.18x10(5).