The effect of limescale on heat transfer in injection molding

With the development of rapid prototyping technologies, injection mold inserts with conformal cooling systems can be manufactured from metal powder by direct metal laser sintering (DMLS). The conformal cooling channels are placed along the geometry of the injection molded product, thus they can extract more heat, and heat removal is more uniform than in the case of conventional cooling systems. But even the most efficient cooling circuits start to wear out, corrosion and limescale depositions precipitate on the wall of the cooling channel, which impede heat transfer from the mold to the coolant. The effect of the depositions cannot be neglected and the modeling of the impact on heat transfer is difficult. We developed a model to investigate the effect of limescale that formed on the wall of the cooling circuit. The thermal properties of the limescale are required for the simulation, therefore they were measured. We concluded that 2 mm thick limescale impedes heat removal so much that the more efficient conformal cooling system can only extract as much heat as the less efficient conventional system.