![]() This is due to the physical property of these liquids to become more viscous as temperature decreases. It will be apparent when you use the calculator that lower temperatures and higher Ethylene Glycol concentrations require a significantly higher flow rate to achieve a given Reynolds Number. We have modified our Reynolds Number Calculator to allow users to select a percentage of Ethylene Glycol and a water temperature and calculate Reynolds Numbers and required flow rates based on these selections. This functionality will be very useful to our industry given the rapidly growing use of pressurized mold temperature controllers, operating at temperatures up to 350☌ (662☏).Įthylene Glycol is a compound commonly used as an additive to water in a cooling system to reduce the freezing temperature of the solution and thus allow circulation of a lower temperature coolant. In the development of our calculator special attention was focused on being capable of calculating values at elevated water temperatures. The Smartflow™ Reynolds number calculator is provided as a service to the injection molding community as an easy-to-use online resource. Increasing flow to gain significantly higher Reynolds number values yields diminishing cooling benefits while using more energy. A factor of 1.5-2.0 is suggested based on our research. It is a good practice in mold cooling to apply a safety factor to ensure that turbulence is well established. But it should be noted that the transition from laminar flow to turbulent flow is also dependent on other factors such as the geometry and roughness inside the flow passages. Engineering handbooks typically indicate that flow is likely to be turbulent for Reynolds numbers above 4000. ![]() Thus Reynolds number has become an important and widely used predictive tool for improving the quality of mold cooling. Molders have learned that superior cooling is achieved when flow is turbulent. In injection molding cooling is typically achieved by circulating a temperature- controlled fluid, usually water, in drilled or machined passages inside the mold. It is important to note that viscosity of a substance typically decreases as its temperature increases, including water! Kinematic Viscosity, γ = A property that quantifies the degree of resistance to flow-for example honey has a high viscosity value and water has a much lower value. Re = (Velocity x Diameter) ÷ Kinematic Viscosity = (V x D)/γĭiameter = the inside diameter of the flow passage At high Reynolds numbers the inertia property of the fluid becomes the dominant factor and flow becomes turbulent, with chaotic eddies, vortices and significant internal mixing.įor flow in a pipe the simplified mathematical expression for Reynolds number is: ![]() At low Reynolds numbers viscous forces dominate and flow is laminar, characterized by smooth flow without internal mixing. Reynolds number is the ratio of momentum to viscous forces in a moving fluid and quantifies the relative influence of these factors for various flow conditions. Osborne Reynolds (1842-1912) popularized the use of this predictive method in the late 1800's and the quantity was named after Mr. ![]() Reynolds number (Re) is a dimensionless quantity used to predict fluid flow patterns.
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