Fundamentals of ice making by convection cooling followed by contact melting

In this paper we show that the production of ice by convection cooling followed by contact melting can be maximized by properly selecting the frequency of the intermittent freezing and removal cycle. In the first part of the paper, this principle is illustrated in three configurations: water freezing inside a tube cooled externally by convection, freezing on the outside of a tube cooled internally by convection, and freezing on a plane wall with convection cooling on the back side. The proper dimensionless groups are identified, and the optimal regime of intermittent operation is reported in dimensionless charts. The second part of the paper focuses on the contact melting process that occurs during the gravitational removal of the ice piece. This time-dependent process is the result of the coupling between the thin-film fluid mechanics, the acceleration of the ice piece and the variable length of the direct contact region. The ice fall time predicted by the contact melting analysis was validated by experiments with ice columns falling from vertical tubes heated from the side.