An Improved Finite Difference Method to Evaluate Heat Transfer in Fuel Pins with Eccentrically Placed Pellets

A method is presented to calculate two-dimensional temperature profiles in fuel pins with eccentrically placed fuel pellets. This is implemented in a finite difference program. By requiring continuity of the radial and angular components of the heat flux vector across the gas gap, an angular-dependent thermal conductivity is derived to account for the eccentric condition. The method is compared with another approach in which the fuel pellet surface is approximated by a “ratchet” boundary. Similar results for temperatures were obtained from both calculations, but the “modeled conductivity” method presented here showed significant gains in computing time and storage requirements.