Evaluation of the Bottom Surface Water Jet Impingement Cooling Rate Using Modified Run-Out Table
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Evaluation of Temperature-Time Profiles by the Lumped Thermal Mass analysis method for bottom surface jet impingement cooling system was carried out. This was done by controlled accelerated cooling using a modified run-out table (ROT). The evaluation was with variant pipe diameters of 10mm - 40mm by a single water jet, having impingement gaps in the range of 55mm - 95mm and controlled sub-cooled to a range of 150oC – 110oC. The results revealed that the cooling rate was faster at an impingement gap of 95mm in all the pipe diameters. This was evident from the plot of temperature-time, with a gap of 95mm showing 1.93oC/s and 3.24oC/s at diameters of 10mm and 40mm respectively. This evidently revealed that at any given pipe diameter the cooling rate is higher at a higher impingement gap for bottom surface controlled cooling. This is also suggested by the calculated heat transfer coefficient that shows an increase with the increase in pipe diameter and impingement gap for an increase in cooling rate. Therefore, for bottom surface jet impingement cooling, a higher impingement gap for any pipe diameter will give a better cooling rate for the steel austempering process.
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