An experimental procedure for validating results of the foregoing problem involves preheating a copper disk to an initial elevated temperature T; and recording its temperature history T(t) as it is subsequently cooled by the impinging flow to a final temperature Tf' The measured temperature decay may then be compared with predictions based on the correlation for NuD. Assume that values of a = 0.30 and n = 2 are associated with the correlation. Consider experimental conditions for which a disk of diameter D = 50 mm and length L = 25 mm is preheated to Ti = 1000 K and cooled to Tf = 400 K by an impinging airflow at Too = 300 K. The cooled surface of the disk has an emissivity of ε = 0.8 and is exposed to large, isothermal surroundings for which Tsur = T∞. The remaining surfaces of the disk are well insulated, and heat transfer through the supporting rod may be neglected. Using results from the preceding problem compute and plot temperature histories corresponding to air velocities of V = 4, 20, and 50 m/s. Constant properties may be assumed for the copper (p = 8933 kg/m3, cp = 425 J/kg ∙ K, k = 386 W/m ∙ K) and air (v = 38.8 z 10-6 m2/s, k = 0.0407 W/m ∙ K, Pr = 0.684).