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moldmakingtechnology.com 25 turbulent flow is present. In fact, a true understanding of the influences on turbulent water flow, pressure and temperature is the starting point to engineering the right water system. Know your Reynolds number. This calculation reveals the minimum needed to achieve turbulent flow. Turbulent flow, which should be your target, occurs at high Reynolds num- bers and is influenced by inertial forces, while laminar flow occurs at low Reynolds numbers and is dominated by viscous forces. Perform finite element analysis (FEA). A predictive engi- neering water FEA is a cost-effective method for collecting data to justify the significant invest- ment of a complex water system. It also can be a great communication tool for mold build- er and molder. Check connections, mold materials and process tempera- ture. After engineering the most efficient heat exchanger possible, you don't want your efforts to be negated when the mold is inserted in the molding machine and connected to the plant's water system, which could restrict water flow. These water systems often include quick connections that reduce the cross-sectional diameter of the water flow and 90-degree fittings that promote pressure loss (standard fluid dynamics principles). Also consider quick connections on the thermalator or chiller, and all related plumbing. Scale, CONTRIBUTOR Rich Oles is owner of ROI Rich Oles Industries LLC. He has 30+ years of experience working directly with injection molders and mold builders in a variety of industries around the world. LEARN MORE Mold Water System Basics Visit short.moldmakingtechnology.com/ water1 for more on the information presented here. Example of a mold water system with (1) connectivity consistency, (2) kinked water fow and (3) a 90-degree ftting and reduced cross- sectional area of water fow. bio-fouling or other foreign contaminants can also restrict flow, or insulate and prevent the efficient transfer of energy from the mold into the water system. Special care should also be taken during mold design and build when using materials with high thermal conductivity for inserts or for the entire mold. When a resin shrinks on to the conductive material, energy moves at a much higher rate than it does when the inserts or molds are made from tool steels. Material hardness is a trade- off, but when handled correctly, the downsides associated with these materials can be minimized or eliminated. Lastly, there are several rules of thumb related to the tem- perature of the water as it flows through the molding system. These include using an engineered water system to cool a part as rapidly as the resin and mold will allow, while keeping dimensional and appearance requirements in mind. There also can be great gains in efficiency by pushing extreme water volumes through an unrestricted water system. In addition, by using materials that are highly thermally conductive, it may be impossible to achieve the recommended delta T of 1°F or less. There are several other considerations for the use of water cooling in plastic injection molding, so the next two articles in this series will discuss plant water systems engineering and plant water quality. FOR MORE INFORMATION: Rich Oles / ROI Rich Oles Industries LLC 616-610-7050 / richoles@gmail.com / Skype: richard.oles 1 2 3