A thin, flat plate 15 cm square is tested for drag in a wind tunnel with air at 30 m/s, 100 kPa (abs), and 16°C flowing across and parallel to the top and bottom surfaces. The observed total drag force is 0.06 N. Using the definition of friction coefficient [Eq. (5.13)] and the Reynolds analogy, calculate the rate of heat transfer from this plate when the surface temperature is maintained at 120°C.

Data from in Eq. 5.13

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From Eq. (5.13), the local friction coefficient is Ts(x) 16(PH) ⁰ ρμ PU Cfx = = 0.6 0.5 = = 0.6( t )us = 0.5 Cf= U1.5 puz = 0.6 Re0.5 Integrating the local value and dividing by the area per unit width (L × 1) gives the average shear 7: = 0.5 ρμ 7 = =- / *0.3 (1²) ⁰5 U15 dx = 0.6 0.6 (ReLx*) 0.5 and the average friction coefficient is therefore T 1.2 pU12 Rel.5 = 0.5 ρμ 6(PH)OSU!.S L