Modeling Convection Boundary Conditions for Ultra-High-Performance Concrete in Cylindrical Columns

In this paper, a numerical model for radial-direction conduction through ultra-high-performance concrete (UHPC) cylinders was developed and experimentally validated. The focus of this research is ultimately to improve understanding of UHPCs thermal behavior, with this portion focused on determining a convection heat-transfer coefficient for appropriate boundary condition modeling. Although constant heat-transfer coefficients are commonly assumed in literature, this paper shows that many commonly assumed constant coefficients overestimate convection performance for natural convection boundary condition environments. For well-studied geometries, numerical solutions including a temperature and time-dependent convection coefficient produced errors under 1%, whereas constant heat-transfer coefficient assumptions produced errors up to 10%. However, for less-common geometries, numerical model errors ranged from 2 to 5%.