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ABOUT THE AUTHOR: Jim Frankland is a mechanical engineer who has been involved in all types of extrusion processing for more than 40 years. He is now president of Frankland Plastics Consulting, LLC. Contact jim.frankland@comcast.net or (724)651-9196. How do you apply this to your process? Each process has to be treated a little differently, but with the same goal—to achieve turbulence at the heat- exchange surface to maximize heat transfer. For example, in a chill roll for sheet/cast film, cooling turbulence is created in the spiral wraps to cool the shell. For blow molds, turbulence is generated in the water passages of the mold. In profile tooling, turbulence is established in calibration tooling. In processes where the tooling does the cooling, the Re can be used to size the cooling channels and even the velocity in the Processing Technologies International, LLC | 2655 White Oak Circle Aurora, IL 60502 | Tel: 630.585.5800 | Fax: 630.585.5855 World Class Sheet Extrusion Systems HVTSE ® DRYER-LESS EXTRUSION SYSTEMS SHEET EXTRUSION TECHNOLOGY LEADER G-Series ® Configurable J-Stack roll stands yield superior sheet performance LIW feeders provide quick formulation set-ups and changeovers TITAN ® Plus control automation for ease of system coordination and control 100% flake feeding capability minimizes regrind inventory build-up Resins: PET, PLA, PP, PS, HDPE... Model: HVTSE ® 105mm-52D Rate: 3,500 lb/hr (1,590 kg/hr) Width: 40 in (1m) Gauge: 15 - 40 mils (0.38 - 1.00 mm) Process: Inline thermoforming Twin Screw by Bandera www.psi-polymersystems.com SCREEN CHANGERS • MELT PUMPS • MIXERS • PACKAGED SYSTEMS What more can you get from your process? • Precise dimensional control • Better melt integrity • Stabilized output • I ncreased yield • Higher use of regrind Industry's most reliable Melt Pump From through-hardened gears to high-wear bearings to leak-free, anti-galling seals, PSI melt pumps provide you consistent, trouble- free performance, year after year. Join the ranks of processors turning to PSI and put us to the test. Discover how much more you can get from your process! Call today to ask for a no-risk trial! 1-828-468-2600 Don't forget to ask about our Pump Exchange program! FROM THE EXTRUDER TO THE DIE - PERFORMANCE GUARANTEED! • www.psi-polymersystems.com • sales@psi-polymersystems.com surface film in the calibration tooling. However, in large cooling tanks it's more difficult to establish turbulent flow. So for pelletizing, pipe, tubing, and some profile applications, it may be hard to signifi- cantly increase the velocity of the cooling water to the turbulent range. In those cases you can use jets, bubblers, or baffles to generate the localized velocity necessary to break up the boundary layer. Even though the temperature of the overall mass of water may remain low, the invisible boundary layer and its temperature gradient surrounding the extrudate restrict heat transfer. In processes where the tooling does the cooling, the Reynold's number can be used to size the cooling channels. 26 JULY 2017 Plastics Technology PTonline.com K now How