A horizontal cylinder is heated electrically. The cylinder is supplied with a current at a dc voltage. Using the data supplied and allowing for both natural convection and radiation, estimate the steady state temperature of the cylinder surface.
A fan is used to blow air over the heated cylinder surface in a cross flow at an average velocity of 50 m/s. Estimate the surface temperature now. The heating is stopped and the cylinder left in the airflow of 50 m/s velocity. Estimate the time for the cylinder temperature by drop by 10K. You will need to find relevant fluid properties, but may assume a surface emissivity of e=0.9. Cylinder diam = 87mm Cylinder length = 254mm Surrounding air temperature = 20C Current = 1.032A Voltage = 20V Specific heat of cylinder =450J/kgK Density of cylinder = 7850 kg/m3
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