Analysis of Convective Heat Transfer from the MAPLE-X Finned Fuel Rod Surfaces

Abstract

The MAPLE (Multipurpose Physics Lattice Experimental) reactor is a new research reactor developed by AECL-Research. The high power density of the MAPLE core requires efficient heat removal, which is achieved by adding fins to the fuel rod surfaces. Although the fins improve the heat transfer performance of the fuel rod, they complicate the subsequent thermal analysis. This paper describes analytical and experimental studies to determine convective heat transfer rates from the finned fuel element simulator (FES). Experiments were performed in an annular test section consisting of the directly heated FES with longitudinal, rectangular fins enclosed in a glass tube. Two FES geometries were investigated. The tests were carried out at pressures between 110 and 350 kPa, velocities from 0.11 to 5.86 m/s, and water temperatures from 26 to 78OC. A two-dimensional finite-element heat transfer model using the Galerkin method was employed in our study to determine nonuniform heat transfer rates along the periphery of the PES surface. The model takes into account thermal properties and variable convective boundary conditions over the FES periphery. Power, pressure, flow, surface and coolant temperature measurements were supplied to the model for each data point analysed. The solution procedure was to alter the heat transfer coefficient on the convective surface until the predicted fin root and fin tip temperatures matched the measured values. A new correlation has been developed based on the computed averaged heat transfer coefficients. Heat flux and surface temperature distributions obtained from the numerical analysis are compared with those calculated from the analytical model described in [I]. Satisfactory agreement has been found between both predictions.