Water spray cooling of profiles right after extrusion is critical for control over the mechanical properties of high strength alloys. To design the optimum distribution of spray, computer simulation is a powerful tool. For that purpose a quantification of the heat-transfer boundary conditions is challenging, especially as the heat transfer coefficient (HTC) changes with the surface temperature. It is possible to record temperature history during the quenching in laboratory/plant experiments and then HTC values can be calculated by means of inverse modeling. These values are applicable only if they are accurate enough. In this paper, it is assumed the maximum allowed tolerance for calculated HTC to be 5%. This work is based on the computer simulation of the real experiments with thermocouples installed inside the sample to estimate the heat flux at the surface of the sample as well as the sample surface temperature using heat transfer equations. Error sources are typically: inaccurate thermocouple positioning and contact quality, sample geometry, thermocouple accuracy and repeatability, thermal properties, initial temperature and etc. In this study, some of these errors and uncertainty sources are selected and their impact on calculated HTC values is investigated. Finally, maximum allowance for every parameter to achieve calculated HTC within ±5% is calculated. Since HTC is not constant but a curve vs. temperature, the calculated HTC values must be between two parallel curves which represent +5% and −5% of nominal HTC.

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