Problem 1 Fig. 1 shows a typical water heater, a), and its heating element, b). The diameter of the heater element/tube is d=15 mm. The total length of the heater tube, including the curved section, is Ltotal=0.5 m. The heater tube-element is positioned horizontally, as shown.
Problem 2 In wind tunnels, powerful fans flow air at high speed through the “tunnel”. The air pressure and temperature are: p=1 atm and Tair=25 C.
The water heater element (used in Problem 1) is being tested in the wind tunnel.
Full power Power =720 W is supplied to the heating element. Calculate the surface temperature
of the heating element, TS_air, while exposed to air flow, Vair=10 m/s.
NOTE: In this problem, use air properties calculated for Tfilm=100 C. Assume emissivity
of the heating element, e=0.5.
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