The effect of liquid solidification at the inner surface of a circular tube upon laminar-flow heat transfer and pressure drop is investigated. Steady-state conditions and a uniform wall temperature, which is lower than the liquid freezing temperature, are assumed. Theoretical solutions for heat transfer, radius of the liquid-solid interface, and pressure drop are determined assuming negligible free convection. Experimentation shows that free convection may produce considerable deviations between theoretical and observed results. A semiempirical method for obtaining approximate solutions is developed. A numerical example which demonstrates how free convection affects the solid-phase shell profile is presented.