Materials Engineering Department
BS in Materials Engineering
The thermal efficiency of evaporative heat exchangers is diminishing due to mineral scale buildup on heat exchanger surfaces. A simulated evaporative heat exchanger was designed and constructed for testing the mitigation effects of polymer coatings on mineral scale deposition rates. The heat exchanger was designed to cool hot mud at 200°F using a cooling water supply with a calcium concentration of 1000 ppm. The system was constructed using 1.5-inch diameter polypropylene piping, a DIG Corporation drip irrigation system, a TotalPond 530 GPH pond pump, an Omega CSI32K miniature benchtop controller, Omega FWH321-020 high temperature heater tape, and fifteen copper pipe samples. DuPont™ lab technicians coated ten copper pipe samples with two different fluorinated ethylene propylene (FEP) polymer coatings: 954G-300 Teflon® FEP and 532-1003 Teflon® FEP. Both coatings were applied to the exterior of five copper pipe samples each (standard 1.25-inch diameter by 1-foot-long). Additionally, five separate foot-long lengths of 1.25-inch diameter copper pipe were used as is. A water solution containing 1 gram of calcium chloride (CaCl2) per 1 liter of water was prepared to achieve a cooling water supply containing 1000 ppm calcium. This water solution was used in conjunction with the drip irrigation system and the pond pump to spray the exteriors of the coated and uncoated copper pipes. The heater tape was used in conjunction with the miniature benchtop controller in an attempt to maintain a pipe temperature of 200°F to replicate hot mud. The simulated evaporative heat exchanger was successful in uniformly delivering highly mineralized water onto heat exchanger pipes; however, the heater tape was unable to provide enough heat energy to maintain the desired temperature of 200°F.