Combined natural convection and solidification in a system of cylinders, arranged vertically in a regular triangular pattern, has been studied experimentally and theoretically. The cylinders were cooled below the solidification temperature of the water. The problem of the unsteady growth of the ice-layer on the cooled cylinders is studied theoretically and an approximate solution has been obtained for the quasi-steady development of the thickness of the frozen layer around the cylinders. In addition the paper also investigates the influence of the contact layer between the ice-layer and the cold surface of the cylinders and its effect on the solidification process. Results are presented and compared between the experimental and the analytical investigation. In general good agreement between the analytical model and the experimental results could be observed for the ice-layer thickness. (C) 2014 Elsevier Ltd. All rights reserved.