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k123loveme
k123loveme
24.03.2020 • 
Engineering

Experiments have been conducted using a metallic cylinder 12.5 mm in diameter and 94 mm long. The cylinder is heated internally by an electrical heater and is subjected to a cross-flow of air in a low-speed wind tunnel. Under a specific set of operating conditions for which the upstream air velocity and temperature were maintained at V = 10.5 m/s and 26.2°C, respectively, the heater power dissipation was measured to be P = 46 W, while the average cylinder surface temperature was determined to be Ts = 128°C. It is estimated that 15% of the power dissipation is lost through the cumulative effects of surface radiation and conduction through the endpieces. The cumulative uncertainty associated with (i) the air velocity and temperature measurements, (ii) estimating the heat losses by radiation and from the cylinder ends, and (iii) averaging the cylinder surface temperature, which varies axially and circumferentially, renders the experimental value of the convection coefficient accurate to no better than 20%.

a. Determine the convection heat transfer coefficient from the experimental observations.
b. Compare the experimental result with the convection coefficient computed from Zukauskas relation and Churchill relation.

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