Turbulent convective heat transfer and radiation is simulated for a hot gas jet, impinging perpendicular on a flat surface at 2 jet diameters away from the jet nozzle. A small solid spherical bead, located in the jet centre half way from the wall, represents a thermocouple sensitive point. The bead becomes so hot that it radiates some heat to the colder surrounding surfaces. This phenomenon is responsible for a gap between the jet temperature and the bead temperature. The jet Reynolds number ranged from 7.67*103 to 4.52*104. Bead sizes 1.0 and 2.0 mm are used in jets at 500°C and 900°C. The simulations show that the mentioned temperature differences are significant and grow rapidly with high temperatures but decrease with Reynolds number. The temperature gap, which can be regarded as the thermocouple measurement error, increases also with the bead size. Simulations can be conducted for specific thermocouples with other shapes and materials to assist the measurement process. The modelling methodology is found to be promising for such demanding simulations that require a fine grid for resolving the field near the bead without using excessive cells in the rest of the domain. Hence, further work in this field is envisaged using the same methodology for solving convection, conduction and radiation in one single model and at a reasonable computational cost together with validating measurements. Hopefully this study contributes to a better understanding of the measurement of hot gas jet temperature and its improvement with the aid of simulations.

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